Inspiration From The Galapagos Islands

From the famous Galapagos Islands comes news about a link between global warming and intensification of El Nino.

 

Imagery- Sentinel 2 Mosaic: Copernicus Browser

El Nino is a pattern of natural climatic variation which occurs when a weakening or reversal of easterly trade winds results in warm Pacific water piling up around the west coast of South America. This phenomenon depends upon subtle interactions between sea surface temperature, ocean currents, and winds, and climate models can’t reproduce these accurately. This means that often different models disagree on how El Nino might be affected by global warming.  Historical records don’t go too far back for us to assess whether there is a clear correlation between global warming and El Nino strength.

Now, a new method uses corals to tease out the temperature of sea water across centuries.

Coral skeletons grow by precipitating the mineral aragonite (CaCO3) in yearly growth bands. Scientists sampled these layers and measured the amount of element strontium and the ratio of heavy oxygen O18 to the lighter O16 in each layer. Aragonite incorporates less strontium and more O16 in warmer water. A sea surface temperature record stretching back a thousand years could be constructed.

The conclusion was that over the past 40 years, temperature swings have become more extreme in El Nino years. This finding from the Galapagos is complimented by another analysis of corals from Kiribati in the Central Pacific. Scientist have a taken a step towards a firmer understanding of the variability of this phenomenon which causes extreme weather events around the globe.

Which other important scientific studies have come out of the Galapagos?

Ahem… there is off course the visit in the year 1835 by a certain Mr. Charles Darwin. His observations there made an important but not an outsized contribution towards his theories of evolution. Darwin was just as comfortable driving home his point using the example of the domesticated pigeon as he was describing the finches and mockingbirds of the Pacific Islands.

Jeff Wallace of the University of Glamorgan in his brilliant introduction to the Wordsworth Classics of World Literature edition of The Origin of Species makes this observation: 

"Readers thus soon find themselves continually shuttled to and fro across the distance between the ‘familiar’ and the ‘other’, the domestic and the exotic, in a text which seems to disdain the very boundary lines between such distinctions. With bewildering and unpredictable variation, we encounter the women-eating barbarians of Terra del Fuego; the small Asiatic cockroach; the thickened stems of the common  and Swedish turnip; the climbing hooks  used by the trailing bamboo of the Malay Archipelago; the egg carrying folds of skin of pendunuculated centipedes; the northern and southern downs of the Weald; the sedimented beds of the mouth of the Mississippi during the glacial period. Darwin’s task at once scientifically central to his work and yet only to be achieved through a vivid and creative use of language, is to make strange or 'astonishing’ the detail of the close and familiar world, and to bring the most extraordinary facets of the alien and unknown within the realms of common understanding. His success, in a text whose fascination is undiminished if not growing as we enter the peculiar concerns of the millennium, lies ultimately in indicating that these contrasting worlds are in fact one world".  

The variation in the beak of the Galapagos ground finches and mockingbirds did inspire Darwin to think about common descent and natural selection, but the legendary finches don’t even feature in his book. The reason is he failed to label his collection systematically! On his return to England he did turn over his collection of wrens, blackbirds, and finches to the ornithologist John Gould.

To his surprise, Gould informed him that despite the great differences in their beak shape and size, the ‘wrens’ and ‘blackbirds’ were in fact all ground finches. His grab bag collection was actually a closely related group of 13 species of finches. Darwin did label his collection of four mockingbirds by island, and they too, as Gould found out, were distinct species. Gould added one more crucial piece of information. All these birds had close but not identical relatives on the American mainland.

Darwin eventually saw the significance of this observation and it became an important piece of evidence for his theory of common descent. He hypothesized that one founder population of these birds must have reached the Galapagos from the South American mainland and then diverged into distinct species on different islands. The standard depiction of an evolutionary tree with branches splitting away from a common node owes its origins to the rather disorganized collection of a wide thinking naturalist and the keen observation of an ornithologist.

Many decades later two scientists did label those finches correctly. And studied them in excruciating detail.

 I am referring to Rosemary and Peter Grant’s epic 40 year study of the morphological evolution of the ground finches of the Galapagos. These two scientists painstakingly measured the variation in beak size and shape over many generations. This they complimented by comparing their genetic differences, and using all this data pieced together a tale of their evolution through changing climate patterns and food availability. Their study has provided a powerful validation of Darwin’s idea that natural selection can shape morphologic change and specialization in populations.

Jonathan Weiner’s Pulitzer Prize winning book, The Beak of the Finch, captures this story vividly. A more updated description of this research has been provided by the two scientists themselves through their publication - 40 Years Of Evolution: Darwin’s Finches On Daphne Major Island.

The Galapagos Islands began forming about 4 million years ago. The Nazca tectonic plate is moving eastwards in the Pacific over a heat source situated deep in the earth’s mantle. The eastern edge of the Nazca Plate is sinking beneath the South American tectonic plate. Sporadic volcanism over the mantle hot spot has created a chain of volcanic islands which become younger towards the west. Volcanoes on the western islands are still active.Today, the islands and the surrounding waters are a marine reserve, offering some protection to its unique biodiversity.

Although geologically young, the specific geologic and bio-geographic circumstance of these islands have proven to be a fertile ground for science. From climate change, to evolution, to conservation biology, scientists working there continue to probe and tease out insights that are proving crucial in navigating the currents of a rapidly changing world.

Darwin- Patagonian Christmas

A friend recently returned from a trip to Patagonia, Argentina. I mentioned to her that Charles Darwin had spent some time exploring the Patagonian coastline and had made some interesting observations about the local fauna and the native people.

Being a bit vague on the details I dug into one of the most reliable source on Darwin's life and work, the Darwin Online archive.  I accessed his Beagle Diary, scrolling down to the time the Beagle docked at Port Desire on December 8, 1833. Below is his entry from December 24, 1833:

24th Took a long walk on the North side: after ascending some rocks there is a great level plain, which extends in every direction but is divided by vallies. — I thought I had seen some desart looking country near B. Blanca; but the land in this neighbourhead so far exceeds it in sterility, that this alone deserves the name of a desart. — The plain is composed of gravel with very little vegetation & not a drop of water. In the vallies there is some little, but it is very brackish. — It is remarkable that on the surface of this plain there are shells of the same sort which now exist. — & the muscles even with their usual blue colour. — It is therefore certain, that within no great number of centuries all this country has been beneath the sea. —1 Wretched looking as the country is, it supports very many Guanacoes. — By great good luck I shot one; it weighed without its entrails &c 170 pounds: so that we shall have fresh meat for all hands on Christmas day.

John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online- Beagle Diary.

As always his keen geology eye had spotted shells which were similar to living shelly creatures, leading him to the conclusion that this region must have been under the sea in the past. All along the South American coastline he noticed oyster and shell beds a meter or two above the current sea level. He concluded that there must have been vertical movement of the crust. 

He was a good hunter too. Apart from the Guanacoe, one of this shipmates shot a rhea. The crew ate that too. Darwin realized only too late that he wanted the entire bird to compare its form to rhea elsewhere in S.America. Eating valuable zoological samples became a common occurrence all through the voyage of the Beagle. 

The Beagle then sailed south to Port Julian. On his walks there Darwin came across bits of spine and hind legs of a largish creature, later identified as a Megatherium or ground sloth. That led him to muse about what could have killed off this variety, as nothing like it existed today. The sedimentary layers entombing the fossil did not indicate any kind of flood. How could an entire species die off?  Taking inspiration from cuttings of apple trees which were clearly part of the parent, Darwin wondered if all individuals of animal species too shared some life force. If so, could a common disturbance or event kill all of them off? 

In February 1834 the Beagle sailed into the Straits of Magellan and Tierra del Fuego. He immediately formed a low opinion of the natives whom he though of as uncivilized savages, living naked and unkempt in an utterly desolate landscape: 

Their country is a broken mass of wild rocks, lofty hills & useless forests, & these are viewed through mists & endless storms. In search of food they move from spot to spot, & so steep is the coast, this must be done in wretched canoes. — They cannot know the feeling of having a home — & still less that of domestic affection; without, indeed, that of a master to an abject laborious slave can be called so. — How little can the higher powers of the mind come into play: what is there for imagination to paint, for reason to compare, for judgement to decide upon. — to knock a limpet from the rock does not even require cunning, that lowest power of the mind. Their skill, like the instinct of animals is not improved by experience; the canoe, their most ingenious work, poor as it may be, we know has remained the same for the last 300 years. Although essentially the same creature, how little must the mind of one of these beings resemble that of an educated man. What a scale of improvement is comprehended between the faculties of a Fuegian savage & a Sir Isaac Newton — Whence have these people come?

John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online- Beagle Diary.

Darwin compared the Fuegian natives with natives he had met further north along the Patagonian coast. Those tribes appeared better dressed, with some European contact spoke a smattering of English and Spanish, and had learned to eat with a fork and knife. 

Could the savage Fuegian change their life habits too? Darwin was doubtful. He thought that hundreds of years of living in this habitat had formed an instinct that could not change, a view reinforced when Jemmy a Fuegian native who had lived with Europeans was seen to have gone back to his native state. Perhaps, Darwin thought,  differences between human populations were more deep than realized.

Much more of South America remained to be explored. At this time his interest lay primarily in geology, but questions about species extinction and fixity, and the nature of human differences in life habits and intellect, lingered on in his mind. 

If you would like to read more about Darwin I will recommend Adrian Desmond and James Moore's fine biography, Darwin: The Life Of A Tormented Evolutionist.

Darwin's House Plants, Water Diviners, Geology Podcast

 A couple of good articles and a geology podcast.

1) “Spontaneous Revolutions” Darwin’s Diagrams of Plant Movement: Darwin's unbounded curiosity for nature led him down many unexpected research pathways. Towards the end of his long career, his restless mind noticed the growth patterns of his house plants. Determined to understand more about their motion and the stimuli, he spent hours tracking tendrils grow and came up with innovative ways to record their movements on paper. Natalie Lawrence has written a lovely essay on this lesser known chapter of Darwin's life and work. 

2) Trust, cost go greater depths to sustain unscientific water divining practice: Large swaths of Indian agriculture is desperately dependent on access to groundwater. Simrin Sirur explores the reliance on water diviners in south India. Diviners use sticks, coppers tongs, coconuts, magnetic compass, and chains with keys as their instruments for sensing groundwater. Despite all this unscientific baggage, many diviners are not all that ignorant. They have a knowledge of the local landscape and groundwater availability. Their prediction relies more on their past experience and a dollop of common sense. 

I must tell you about my experience with a diviner. My neighbor requested that I accompany her to a plot of land outside Pune. She had hired a diviner to help her locate groundwater. We picked him up en route. He was the late Pandit Bhimsen Joshi's son! On reaching my friend's property he got to work with copper tongs. After a few minutes of walking  up and down the site the copper tongs started shaking. He indicated the spot to drill and suggested going down to a depth of 150 feet. On the way back he cheerfully told us that he knew that the adjacent plot owner had struck water at 150 feet. Past experience and common sense go a long way! 

3) Geology Bites Podcast:  Conversations with Geologists: Oliver Strimpel has had quite an unusual career beginning with a doctoral degree in astrophysics. He later became the director of the Computer Museum in Boston and then a patent attorney. But geology beckoned him. He has worked alongside geology researchers trying to date rocks and unravel the timing of movement of the Karkoram fault in Ladakh. Geology Bites grew out of his passion for the subject. You will find a wide range of geology topics discussed on this site. 

I have so far listened to experts talk about radioactive waste disposal, continental crust composition, the inherent bias in the global sedimentary record, and on the evolution of minerals through geologic time. All have been excellent. The talks are about half hour, so they don't tax your patience too much. 

If you have free time coming up this Diwali, I recommend you dive into this collection of geology talks.

Evolution Through Punctuated Equilibrium: History Of An Idea

Palaeontologist Niles Eldredge explains how one of the most famous papers on paleontology and evolution came to be published: 

Steve was determined to be a part of Tom’s plan to do a GSA symposium and publish a book of essays on this new-fangled concept of “paleobiology.” Tom had a list of topics and was shopping around for speakers to be assigned to each one. When Steve saw the list, he told me that he had first wanted “morphology”—but that was already assigned to Dave Raup. So he opted instead for “phylogeny”—but that had been grabbed up by Mike Ghiselin. That left only “speciation,” the last of the evolutionarily imbued topics on Tom’s list, as yet unassigned. Steve called me up, explained the situation, and said he had settled for speciation—but could not think of anything much to say about it beyond the manuscript I had written and recently submitted to Evolution—there of course being no Paleobiology as yet. “The Allopatric Model and Phylogeny in Paleozoic Invertebrates”—a distinctly un-Gouldian, plodding, if accurate, title (Eldredge 1971). Without Ralph Gordon Johnson in the editorial chair of Evolution at that time, I doubt that that early paper would have been accepted. As it was, it was likely to have gone relatively unnoticed—had not Tom come along, Steve grabbing “Speciation”—and Steve asking if we could coauthor the paper along the basic lines of my first effort. He was stuck with “speciation,” and couldn’t think of anything much to say beyond what I had said in the Allopatric Model manuscript.

This passage is from an article by Niles Eldredge titled Reflections On Punctuated Equilibria, published in a recent issue of Paleobiology. The 1972 paper he refers to, coauthored with Stephen Jay Gould, was, Punctuated equilibria: an alternative to phyletic gradualism. It marked the beginnings of a long debate on how to interpret the patterns of morphological change observed in the fossil record. Do species remain in stasis, showing little morphological change through much of their existence as Eldredge and Gould argued? Do periods of rapid morphological change coincide with the origin of new species (speciation)? Supporters hailed it as a revolutionary work. Critics called it 'evolution by jerks', a jibe aimed not just at the patterns of change.

Dr. Eldredge provides a very insightful look at the history of this idea including some fascinating snippets on Darwin's thinking about divergence and species origins. For Darwin, change accumulates incrementally over long passages of time. Divergence via natural selection can give rise to descendant varieties even without geographic isolation of a population. Later thinking has given more importance to exogenous factors like climate change in causing habitat fragmentation and reproductive isolation. Populations gets geographically isolated first, and then diverge from the ancestral species either through natural selection or random genetic drift. Eldredge and Gould applied this idea to the fossil record and emphasized that the sudden appearance of new fossil species is a manifestation of long periods of stability interrupted by episodes of isolation and geologically rapid shifts in morphology (allopatric speciation).

There is a lot to take in and think about the long term patterns of change preserved in the fossil record. But it is enriching reading. The article is open access.

Patterns Of Angiosperms And Insect Evolution

Charles Darwin famously called it an 'ábominable mystery'. He was referring to the sudden appearance and diversification of flowering plants in the Cretaceous fossil record. He noticed that these early fossils resembled modern flowering plants. 'Primitive' or ancestral stages were missing. Today, biologists categorize these as crown and stem representatives of a group. 

The first fossil evidence of flowering plants is from 140-130 million year old sediments. These are early types of pollen grains with one aperture (uniaperturate). Triaperturate pollen is found in slightly younger 125 million year old rocks. Towards the end of the early Cretaceous, by around 100 million years ago, flowers, leaves, and other organs appear from several continents representing all the major groups of angiosperms.

The picture below is of an early Cretaceous (~100 million year old) flowering plant from the lotus family. The location is northeast Brazil. There is a remarkable preservation of the whole plant, with connected roots, rhizome, leaves, and aggregate fruit. 

Source: William Vieira Gobo et.al. Nature Scientific Reports 2023- A new remarkable Early Cretaceous nelumbonaceous fossil bridges the gap between herbaceous aquatic and woody protealeans.

Taking a long view of their evolutionary pattern, angiosperm diversification is structured in three phases. The first phase was a steady expansion through early to late Cretaceous. There was more rapid diversification in late Cretaceous by around 70 million years ago. Enumeration of floral species through the Cretaceous indicate that angiosperms made up about 5% of species in early Cretaceous, increasing to 80% by Maastrichtian times (late Cretaceous). Despite this increase in species numbers, in terms of biomass, angiosperms were still a small component of Cretaceous floras. Their domination of floral communities, including the origin of modern wet tropical forests, began in the Paleogene (65-24 million years ago) after the end Cretaceous mass extinction. Michael J. Benton, Peter Wilf, and Herve Sauquet have provided a good overview in New Phytologist of this pivotal phase of ecosystem change.

These evolutionary changes did not occur in isolation. Throughout the Cretaceous, significant changes were occurring to terrestrial ecosystems, with the origination of many plant and animal groups. This extended phase of ecosystem reorganization is known as the Cretaceous Terrestrial Revolution. Angiosperm diversification is thought to have played a key role in this transformation of land biodiversity, so much so, that the phase from about 100 million years to 50 million years ago is known as the Angiosperm Terrestrial Revolution.

The Cretaceous -Paleogene mass extinction hit angiosperms hard, as well as altering the trajectory of their evolution. For example, there was a 40% loss of diversity of flowering plants in Colombia following the mass extinction. But certain attributes of angiosperms, such as their partnerships with other organisms, their ability to efficiently capture energy and enhance photosynthetic rates, and an underlying genetic propensity to speciate, resulted in them expanding rapidly in the post extinction landscape. Angiosperm evolution opened up opportunities for a variety of land creatures including insects, spiders, lizards, birds, and mammals,  eventually driving up terrestrial biodiversity to 10 times more as marine biodiversity.

Paleobiologists are interested in understanding the interaction and impact angiosperm diversification could have had on other groups of plants and animals. Of particular interest is the diversification of insects in the Cretaceous and Paleogene.

Modern insect lineages began diversifying by 245 million years ago, long before angiosperms evolved. Gymnosperm and insect communities preserved in amber and sediments show that insects had an intricate relationship with host gymnosperms like cycads, conifers and ginkgoaleans.  Insect pollination of gymnosperms predated the origin of angiosperms by at least 100 million years and their fossil record show phases of diversification even when angiosperms were rare. 

Did angiosperm evolution also drive a rise in insect diversity? Pollinator insects particularly would seem to benefit from an abundance in flowering plants, and if so, what co-evolutionary patterns are apparent from the fossil record?

David Perise and Fabien Condamine have tackled this question in a new study in Nature Communications. I will share this beautifully compiled infographic from the paper that conveys so clearly the patterns of angiosperm and insect diversification through the Cretaceous and Cenozoic.

Digging into published databases, the researchers compiled data on the origination and extinction times of angiosperm and insect families. They then statistically analyzed whether angiosperm and insect origination and extinction times, and pulses of their diversification coincide. Their analysis showed that angiosperms seemed to have played a dual role in insect evolution. They mitigated insect extinction through the Cretaceous and spurred on the origination of new insect groups in the Cenozoic. Besides a broad analysis of insects, they also found that pollinator insects like bees and long proboscid butterflies show a pronounced diversification alongside angiosperm lineages. 

The success of angiosperms in the late Cretaceous and Cenozoic coincided with the decline in gymnosperms. Intrinsic mechanisms of genomic rearrangements in angiosperms resulted in repeated evolution of novel traits and specializations. They competitively displaced gymnosperms. The impact on gymnosperm dependent insects was variable. Generalist insect pollinators such as several beetle lineages transitioned to angiosperms. Much of the co-diversification of angiosperm and insects can be explained by this shift of gymnosperm pollinators to angiosperm hosts.  Gymnosperm specialized insect groups did not fare that well. For example, gymnosperms like Cheirolepidiaceae and Bennettitales went extinct by the latest Cretaceous. This was followed by the extinction of insect groups that were dependent on these plants such as some specialized long-proboscid flies, scorpionflies and lacewings.

Insect diversification did not depend only on angiosperms. Analysis also shows that warmer climate phases negatively impacted insect diversity and coincided with higher insect extinction rates. There seems also to be a relationship with other plant types. Spore plant and gymnosperm diversity had a positive impact on origination rates of insects. Ecosystem relationships and dependencies are multifarious and complex as this analysis between angiosperm and insect co-evolution shows.

Darwin's anxiety over flowering plants reflected his insistence that evolution is gradual. Nature does not make leaps, he stressed. He explained abruptness in the fossil record by invoking missing strata due to non deposition and erosion. Regarding flowering plants, he suggested that fossils were perhaps preceded by a period of cryptic evolution of that lineage that took place in a remote area or a lost continent, although he conceded that this was a poor explanation. However, this latter view, that a substantial lag time or a long fuse precedes the bang, continues to resonate among many biologists. Molecular methods that compares accumulated genetic difference to calculate the time of divergence of groups indicate a fairly long gap between the genetic branching of lineages and their first fossil appearance. 

Most familiar is the example of the origin of animals. Molecular data indicate that animals originated by 750 million years ago, yet unequivocal animal fossils appear by 570 million years ago, close to 200 million years later. Similarly, some molecular estimates put angiosperm origins to pre-Cretaceous times, stretching back 240-200 million years ago to Triassic-Jurassic, a good 100 million to 60 million years before first appearance of fossils.

This idea of a phylogenetic fuse has been recently criticized. Published in Systematic Biology, Graham E. Budd and Richard P. Mann have undertaken a critical examination of molecular clock methods. Their analysis indicate that popular methods used to assign probabilities to maximum age of lineages are biased against rapid lineage radiations being true evolutionary events. In their view, the mismatch between molecular dates of lineage origin and the timing of the first appearance of their fossils is an artifact. They point out that the coincident appearance of fossils from widespread localities in a particular sequence and across different modes of preservation faithfully records evolution. The time gap between the origin and later diversification of lineages is not that deep.

The 'abominable mystery' of the sudden appearance of fossil groups may in fact be a real biological motif in earth history, signalling the rapid radiation of lineages filling ecologic spaces following an environmental crises and evolutionary innovation.

Darwin's Earthworms, Ocean Currents, Geology Heritage Lost

My latest set of readings.

1) Why Darwin Admired the Humble Earthworm. A delightful essay by Philip Ball on Darwin's work on earthworms. Published towards the end of his career, this book apparently sold more copies than the Origin of Species! As Philip Ball wittily observes, that tells us something about the English passion for gardening. Darwin's research on earthworms consisted of detailed observations and cleverly designed experiments, often carried out with the help of family members. 

His powers of observation and analysis remained undimmed - "Darwin reported that 80 percent of leaves he removed from worm burrows had been inserted tip first—a far from random distribution".

2) No, the Gulf Stream isn't going to shut down. The premise of the movie The Day After Tomorrow is that of a catastrophic cold snap engulfing north America and Europe, triggered by the shutting down of the Gulf Stream. This massive ocean current forms in the subtropics in the western side of the Atlantic and transports heat from the lower latitudes to northern Europe, moderating the temperatures in these northern regions. Media reports claim that recent work might be pointing to a collapse of the Gulf Stream, but as Frank Jacobs explains, people are conflating two very different current systems. 

Some studies are suggesting that the Atlantic Meridional Overturning Circulation, a much smaller and restricted circulation system, might be slowing down and might even collapse by 2050. This will result in some cooling in the Greenland and Norwegian seas, but will not affect the larger Gulf Stream. The article has a nice animation of global ocean currents which I found informative.

3) They Have Put Geology in Coffins. For long, geologists have been complaining about the utter indifference shown by successive Indian governments to our natural heritage. Here is one more example from Himachal Pradesh. Along the Kalka-Shimla highway, on the stretch between Parwanoo and Solan lay a treasure. This was a section of sedimentary rocks recording the retreat of the Tethys Sea which began after the collision between India and Asia started creating high topography. Along this stratigraphic section, marine sediments give way to freshwater deposits. The outcrop was a natural outdoor laboratory for students and researchers. Now it is gone. The National Highway Authorities of India has covered it with concrete and stone walls. Science is the big loser again. 

Arundeep Ahluwalia expresses the anguish of geologists who knew and loved this part of the Himalaya- "It forever denies coming generations any chance to study the long stretches of such highways and to the nature lovers in society the excitement of the history and grandeur of the earth".  

Read and weep. 

Links: Birth Of Species, Children's Book, Rise Of Oxygen

 Some geology and evolution material for your perusal.

1) I came across this well crafted documentary by Niles Eldredge and Stefano Dominici on the history of the development of ideas on the birth of species. It is a paleontologist's perspective with fossils being given the centre stage. A great many personalities who contributed to the early thinking on the origin of species are featured. Among the prominent ones who influenced Darwin were Lamarck, Cuvier, Giambattista Brocchi, and John Herschel to name a few. Completely left out of this film is Alfred Wallace. 

It does center around Darwin, and, later towards the end, on Niles Eldredge's work on Punctuated Equilibrium, which he published in collaboration with Stephen Jay Gould. I have often wondered whether there was any tension between Eldredge and Gould regarding proprietorship over Punctuated Equilibrium given Gould's very bombastic advocacy of this idea. The last section of this film is revealing! 

Beautifully compiled. Do watch. 

 

If  you are unable to access the embedded video, view it at this permanent link - The Birth of Species. 

2) Zircon (zirconium silicate) is a remarkable mineral. Born in the cauldron of magma chambers, it is henceforth virtually indestructible unless it is melted down again. This makes it a witness to geological processes affecting and shaping terrains over hundreds of millions of  years. What a story it has to tell us. And that is precisely what geochronologist Matthew Fox has done. He has written a children's book titled Jane's Geological Adventure, which follows Jane, the zircon grain, from her birth in a magma chamber to a life lasting 400 million years. Alka Tripathy-Lang reviews the book.

Meet Jane, the Zircon Grain—Geochronology’s New Mascot.

3) Elizabeth Pennisi writes about a new paper published in Nature Geosciences on the link between the increase in the length of the day and the rise of atmospheric oxygen on early earth. 

‘Totally new’ idea suggests longer days on early Earth set stage for complex life.

Darwin: Caught Between Catastrophism And Gradualism

This past Saturday was Guru Purnima and I thought I would share a short post on two of Charles Darwin's mentors who had a big influence on him particularly in the early days of his scientific career. Adam Sedgwick and Charles Lyell were both geologists whom Darwin looked to for advice and inspiration. Although Darwin had a rather broad training in natural history, he initially considered himself a geologist. 

Just before embarking on his voyage aboard the H.M.S.Beagle in 1831, Darwin had spent some time doing fieldwork in Wales with Sedgwick. Over a couple of weeks Darwin became proficient in identifying rock types, describing outcrops, and mapping and interpreting the regional geology. He first met Charles Lyell after he returned from his voyage in 1836, although he had been regularly corresponding with Lyell about geology. 

Adrian Desmond and James Moore's biography Darwin: The Life of a Tormented Evolutionist has a lovely description of Darwin's early encounters with geology as he began his travels aboard the Beagle with the shadow of Sedgwick and Lyell following him around. 

The Beagle has reached St. Jago in the Cape Verde Islands, about 300 miles off the African coast. There Darwin saw a fossil bed, rich in shells and corals, about 30 feet above sea-level. 

An extract from Desmond and Moore's book: 

" Sedgwick in North Wales had inducted him into Cambridge-style geology- a science of violent crustal movements,wrenching strata, and mountain thrusts. But how had this seashell band arrived at this height above the ocean? Lyell's Principle's of Geology could help here, even though Henslow had said to beware. Lyell pictured a world constantly and slowly changing, with the past no more violent than the present - so that today's climates,volcanic activity, and earth movements balance one another, land rises in one area as it falls in another, not cataclysmically, as Sedgwick thought, but gradually".

 Darwin studied the fossil band and reasoned that the sea itself could not have fallen over the lifetime of St Jago islands (he was wrong in this assumption, but at that time the causal link between short term climate change and sea-level fluctuations was just not appreciated). The fossil layer did not exhibit any signs of a violent geological change. He decided a gradual uplift of the volcanic island was a better explanation for the stranded fossil bed.

Darwin became and remained a gradualist throughout his lifetime. Gradualism was one of the central ideas of his theory of evolution. That biological change too proceeds slowly was something he had imbibed from Lyell's thinking about geological processes. 

His geological observations about South America were well received by his two heroes. Lyell introduced him to Britain's science elite and Darwin quickly received invitations to join various Geological Societies. He was ready to embark on a serious geology career, but a nagging question about the nature of life eventually took him on a different path. 

His work on transmutation began consuming him as he wholeheartedly devoted his research energies to solve the 'mystery of all mysteries'; how do new species originate and change?  Even after he drifted away from any serious geological work, Darwin remained a close friend with both his mentors. But neither ever embraced his theories of evolution. Sedgwick and Lyell, rooted in Anglican tradition, could not shake of their religious convictions and accept a naturalist explanation for life that Darwin had proposed. 

 Sedgwick was particularly severe in his criticism. He wrote on reading The Origin of Species (quoted from Desmond and Moore's book):

.." Parts of it I admired greatly, parts I laughed at till my sides were almost sore, other parts I read with absolute sorrow because I think them utterly false and grievously mischievous. You have deserted... the true method of induction,and started in machinery as wild, I think, as Bishop Wilkins's locomotive that was to sail with us to the moon".

Sedgwick and Lyell's cold shouldering of his theory caused Darwin immense pain. He had always felt at home with the geology community of Britain whom he thought of as more of a gentlemanly fraternity than the cantankerous zoologists. Desmond and Moore describe how physically sick  Darwin felt after a futile conversation with Lyell about his ideas on transmutation. Shivers, shakes, fever, vomiting became routine maladies throughout his later life, manifestations of the inner turmoil of working on an extremely unpopular theory.  But the dogged and outstanding scientist that he was,  he could not and did not let his mentor's rejection persuade him to stop his work or change his thinking. Patiently and 'gradually'  he put the pieces together and built a body of work that changed the world forever. 

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Darwin's Atolls - Beneath The Idyll

 I've expanded on the link I posted last week on Darwin's Atolls. 

A beautiful theory has been undone by ugly facts...well, let's just say facts.

How do coral atolls, those shimmering ring shaped islands set against the blue tropical ocean, form? Charles Darwin had pondered this question on the H.M.S. Beagle as she sailed across the Pacific and Indian Oceans in the early 1830s. He famously reasoned that coral colonies begin growing in the shallow waters surrounding oceanic volcanoes. Eventually the volcanoes sink into the ocean, while the coral keep growing upwards. The central area where the volcano existed becomes a deep lagoon, surrounding by a ring of coral reefs. 

 But he just assumed that the present day corals atolls are growing on a volcanic foundation.

Actually, most are not. Tropical region atolls rest on an earlier generation of coral and limestone. These in turn have grown on an even earlier layer of coral growth and so on through the past few million years.

Darwin at that time didn't know that the climate over the past 2.6 million years had shifted periodically between glacial and inter-glacial phases resulting in sea level changes. The story begins in the Pliocene around 5 million years ago. A long period of sea level stability resulted in reefs and other calcium carbonate sediments accumulating on the shallow waters above sea floor ridges. Thick deposits formed flat topped carbonate banks. The earth's climate began to change around 2.6 million years ago as polar and high latitude ice sheets expanded and then withdrew. As a result, sea level started falling and rising cyclically. 

These repeated sea-level fluctuations amplified around half a million years ago. When sea level fell, rain water dissolved the exposed carbonate flats to form an uneven karst topography comprising a depressed bowl with an elevated rim. Subsequently, when sea level rose, new coral growth began in the optimal water depths above this jagged limestone rim. With every sea level fall and rise, erosion and new coral growth accentuated the relief between the central depression which became the lagoon and the rim which was now made up of towering stacked coral reefs. The modern looking atoll evolved in this manner.

A recent detailed study by Andre Droxler and Stephan Jorry compiling decades of research on the Pacific Ocean and Indian Ocean reefs demonstrates this elegantly.

The image above shows a portion of the Chagos atolls in the Indian Ocean. Notice how the rings of coral reefs have formed on a submerged flat 'mesa' or table land. These are the vestiges of the carbonate banks that formed during the Pliocene and later became the foundation for the modern atolls.

Great scientists get it wrong frequently too. Darwin erred in his too loyal adherence to the principle, 'Present Is The Key To The Past'.

He observed that some volcanic islands have coral colonies growing around them. He extrapolated this condition to the past and theorized that atolls began as reefs fringing volcanic islands. He couldn't imagine how otherwise corals could grow in the middle of the ocean without them having a shallow water foundation to colonize.

Uniformitarianism has been a very helpful paradigm in understanding many aspects of the past, but geologists have learned to apply it with caution. During the long 4.5 billion year history of our planet, critical combinations of atmosphere and ocean compositions and continental configurations coupled with the evolving biosphere have resulted in unique geologic products and processes which have no modern analogue.

Darwin's atolls offer us some lessons about our future too. Ten thousand years of relative climate stability has allowed civilization to flower, but has also lulled us into a dangerous complacency about nature and its permanence. The idyll of these atolls is ephemeral. Their very foundations are testimony to rapid environmental change and great dyings of marine ecosystems. Such changes await us in the future too, now hastened by our own agencies.

Several hundreds of years from now our descendants may well be looking on at a planet where many of Darwin's atolls have disappeared under the sea and our forests and croplands diminished by fire and dust. Will it be possible to modulate this coming change? For that, we must heed the signals from our geological past. Our present behavior will be the key to our future.

A more detailed write up about Andre Droxler and Stephan Jorry's work has been posted on the Rain to Rainforest Media website - If Darwin only knew: His brilliant theory of atoll formation had a fatal flaw.

Readings: Darwin's Atolls, Pre Toba Humans, Herbivore Diets And Ecology

Posting some interesting readings:

1) A beautiful theory has been undone by ugly facts. How do coral atolls, those shimmering ring shaped islands set against the blue ocean, form? Charles Darwin had famously reasoned that coral colonies begin growing on the slopes of volcanoes. Eventually the volcanoes sink into the ocean, while the coral keep growing upwards. The central area where the volcano existed becomes a deep lagoon, surrounding by a ring of coral reefs. But he just assumed that the present day corals atolls are growing on a volcanic foundation. Actually, most are not. Tropical region reefs and atolls rest on an earlier generation of coral and limestone. These in turn have grown on an even earlier layer of coral growth and so on through the past few million years. 

Darwin at that time didn't know that the climate over the past 2-3 million years had shifted periodically between glacial and inter-glacial phases resulting in sea level changes, and how these repeated sea-level fluctuations can create environments where corals grow during a sea level rise or later dissolve during a sea level fall to form a karst landscape. This jagged uneven surface in turn becomes the foundation for a new generation of corals. A new detailed study of the Pacific Ocean and Indian Ocean reefs demonstrates this elegantly.

Paper- The Origin of Modern Atolls: Challenging Darwin's Deeply Ingrained Theory.

Write up - Darwin's theory about coral reef atolls is fatally flawed.

2) Did Homo sapiens enter India prior to the devastating Toba eruption that took place about seventy four thousand years ago or after? This question is of interest in elucidating the timelines and dispersal routes of our species from Africa. Homo sapiens had reached Australia by around 60,000 years ago with India being one obvious migration path.  There are no skeletal human fossils from this time period in India and stone tools have been variously interpreted as belonging either to Homo sapiens or an earlier archaic human. There were few accurately dated sites from the time period of 80,000 years ago to 50,000 years ago. Now, some new work from the Son Valley, Madhya Pradesh, shows long term human occupation in north India from pre Toba eruption times. The layers containing stone tools span from about 79,000 years ago to 65,000 thousand years ago. The tools resemble those from the Middle Stone Age of Africa, Arabia and Australia and are interpreted to have been the handiwork of Homo sapiens. 

Paper- Human occupation of northern India spans the Toba super-eruption ~74,000 years ago.

3) The ecologic context of the evolution of our genus Homo is of great interest. A recent study focuses on using carbon isotopes to tease out dietary shifts in herbivore fauna living in East Africa in the late Pliocene to Early Pleistocene. Analysis of herbivore teeth from 3.6 million years ago to 1.05 million years ago reveals a shift from C3 derived food (woody vegetation) to C4 derived food (grasses), first around 2.7 million years ago and again later around 2.1 million years ago.  Woodlands were giving way to more open savanna, a change that coincides with the evolution of Paranthropus and Homo. 

Paper- Dietary trends in herbivores from the Shungura Formation, southwestern Ethiopia.

Write up - Researchers use fossilized teeth to reveal dietary shifts in ancient herbivores and hominins.

 

Darwin: Citizen Science

After his return to England in 1836 from a five year round the world trip aboard the Beagle, Darwin did not travel again for any extended fieldwork. His home became his study and his laboratory, but he was no lonely isolated genius. His ideas stemmed from data that streamed in from all over the world.

From Darwin: The Life of a Tormented Evolutionist

Down House had become the hub of a correspondence network across the Empire, its tentacles touching every little England. The sack of mail brought gems daily to aid his sexual selection. Botanists from Ceylon to Calcutta sent reports on monkey manes and bearded Indians; mining engineers from Malacca to Nicaragua told of indigenous customs; tile manufacturers in Gibraltar attended to merino lambs; wine exporters in Portugal followed the local tailless dogs; Laplanders measured reindeer horns; New Zealanders heroically tackled the Maori's sense of beauty; and missionaries and magistrates from Queensland to Victoria ceased converting and incarcerating to observe aboriginal ways- with an old Beagle shipmate Philip King helping out. This is what Darwin excelled at: collecting and collating, tracking down facts, verifying,extending his old notebook speculations to embrace the globe.

Darwin had many India connections. His botanist friend Joseph Hooker who had traveled to India in the 1840's had been one source of information on indigenous plants, animals, and people. From 1855 or so, Edward Blyth, curator of the museum of the Royal Asiatic Society in Calcutta became his chief contact. He struck up a lively correspondence with Darwin. Details about monkey manes and bearded Indians would have come from him.

"his large and varied stories of knowledge, I should value more than that of almost anyone" he wrote of Blyth.

Vikram Doctor has written an insightful essay on Edward Blyth's life. It sketches the sharp contrast between the financially comfortable life Darwin lived in England against the hardscrabble existence of Blyth, who managed to stay on for 21 years in India on a salary of Rs 250 a month, supplementing it with a trade in exotic birds and animals.

A love for natural history drove Blyth on and Darwin benefited from that immensely.

Darwin: Victorian Menage A Trois

In 1864, a few years after the publication of the Origin of Species, Darwin, fighting a bout of illness took up some botanical work on Lythrum, a genus of flowering plants known as loosestrifes. He had been breeding them on and off for many years. His interest was in their sexuality as they gave him a deeper understanding on the evolution of sterility and reproductive isolation. His theory of population divergence and the origin of new species depended upon the evolution of traits that prevented individuals and populations from mating with each other.

Lythrum was known for its triple sexuality. There were three kinds of flowers. The female stigma could be tall, medium or short-styled. Each was accompanied by two sets of male stamens.  If the female was tall, the males were short or medium sized.

Darwin realized through his breeding experiments that greater the difference in height between these sexual organs, the greater the frequency of sterility. Mating between the unequal sized sexes in the same plant produced sterile seeds.  This was evolution preventing inbreeding and favoring cross pollination.

Adrian Desmond and James Moore in their biography, Darwin: The Life of a Tormented Evolutionist, write about Darwin's mischievous side:

" Talk about illegitimacy might have shocked the ladies guilds, at least coming from Erasmus Darwin's grandson. (Grandfather's own bastardizing experiments were still supplying tittle-tattle. At this moment Darwin suspected the widow of a botanical friend, Francis Boott, to be an illegitimate granddaughter of old Erasmus). But Darwin was stolid, methodical, reducing the love of the plants to cold, clinical calculation. Sterile seeds counts somehow fitted an unromantic, data-crunching age. Not for him Erasmus's flowery personifications, as styles and stamens bent to embrace in a kiss:

Two knights before thy fragrant altar bend,
Adored Mellissa! and two squires attend.

Still, he could tease. Solicited by a Mrs Becker for something edifying for her ladies' literary society, he posted 'On the Sexual Relations of the Three Forms of Lythrum salicaria'. Goodness knows how many red faces left after hearing that 'nature has ordained a most complex marriage-arrangement, namely a triple union between three hermaphrodites,- each hermaphrodite being in its female organ quite distinct from the other two hermaphrodites and partially distinct in its male organs, and each furnished with two sets of males' ".

There is no doubt that Darwin was an outstanding thinker. But he also was a hands on guy. His thinking was not vacuous or overly speculative.  He was a tinkerer and putterer.  He produced data. By cross breeding plants. By dissecting barnacles. By co-opting pigeon breeders and noting down the variation in the size and shapes of different breeds. Documenting tiny differences between individuals within groups was crucial to his case that complex structures could evolve by incremental changes over generations.

From life's little details he built the grandest theory of all.

Aristotle And Darwin: Why?

A thought provoking passage from The Lagoon: How Aristotle Invented Science by Armand Marie Leroi-

The history of Western thought is littered with teleologists. From fourth-century Attica to twenty-first century Kansas, the Argument from Design has never lost its appeal. Aristotle and Darwin, however, share the most unusual conviction that though the organic world is filled with design there is no designer. But if the designer is dead for whose benefit is design? It's the prosecutor's question: cui bono?

Darwin answered that individuals benefit. Biologists have batted the question about ever since. The answers they've essayed are : memes, genes, individuals, groups, species, some combination or all of the above. Aristotle, however, generally appears to agree with Darwin: organs exist for the sake of the survival and reproduction of individual animals. This is why so much of his biology seems so familiar.

Yet there is a deep difference between Aristotle's teleology and Darwin's adapatationism, one which appears when we follow the chain of explanation that any theory of organic design invites. Why does the elephant have a trunk? To snorkel. Why must it snorkel? Because it's slow and lives in swamps. Why is it slow? Because it's big. Why is it big? To defend itself. Why must it defend itself? Because it wants to survive and reproduce. Why does it want to survive and reproduce? Because..

Because natural selection has designed the elephant to reproduce itself. Darwin gave teleology a mechanistic explanation. He halted the march of whys.

Aristotle was an eternalist. In his cosmos, organic beings were produced by a union of their parents. They in turn by a union of their parents.. continued into infinite regress. Organisms wanted to survive and reproduce so that their "kind" persist for ever. This static world had always existed. He saw divinity in immortality.

In Aristotle's world organic beings don't change and transform into anything else. He never did come around proposing a theory of transmutation or change or evolution. He had some of the raw material to advance such thoughts.

His extensive dissections and comparative anatomy had given him an understanding that life is arranged in a hierarchical manner. Dogs and foxes are more closely related to each other than either is to lions and leopards. Both, canids and felines though are part of a larger mammal family. Members within this family are more similar to each other than they are to members of reptiles. Aristotle recognized that there are groups within groups. He termed the basic taxonomic units as genos. These are part of the larger magiste gene. Ikthis (fish), entoma (insects),ornis (birds), zootoka tetrapoda (live bearing tetrapods- mammals), oiotoka tetrpoda (egg laying tetrapods -reptiles, amphibians) were some of his "greatest kinds" or  magiste gene.  Yet, he didn't ponder upon the relationship between life's groupings and never realized that this pattern is a tree like structure, resulting from common ancestry and subsequent lineage branching. The figure to the left is Darwin's sketch (Notebook B 1837) of the tree of life depicting common ancestry and the branching nature of life.

Aristotle was aware that there is variation within each "kind" or genos. Organisms within a genos varied in their eidos or form. He also had a theory of inheritance. Parents passed on their eidos to progeny, often not exactly. Progeny then, occasionally, could be somewhat different from parents. Moreover, his understanding of inheritance was surprisingly modern. A child might inherit her father's nose or her mother's nose but not something in between. So, he had a particulate view of inheritance. This also meant that traits remain stable and may pass on unaltered over many generations.  Father's and mother's contributions don't blend to form some average feature, but remain discrete. By this he did not mean that actual particles were being transmitted. Rather, traits were reproduced by the movement and heat of either the semen or 'menses' (menstrual fluid). Whichever was stronger determined whether the child resembled her father or mother.

Darwin never understood inheritance very well. He was sure that variation is the  fuel of evolution. But he was troubled that blending would wipe out variation in populations. He struggled with the problem of inheritance for decades.

Aristotle's limitation was that he didn't think anomalous features or differences offered any advantages to the individual. His view was that creatures are born within the limits of their physiology and there was no room for improvement. In that, he should have listened to Socrates! In a Greek society with very particular notions of beauty, Socrates, with his snub nose and flabby lips was an anomaly. He boasted though that his lips worked better than anyone else's. The mutant feature provided an advantage. Aristotle rejected such notions.

Perhaps this is why he couldn't take the next step.... That advantageous variation could be selected upon by nature. Possessors of that trait would on average leave behind more progeny. A certain new form would thus become more common over generations and while some other form disappeared. Some people argue that the lack of a fossil record may have been one reason why Aristotle never appreciated that organic beings have changed over time. However, as Leroi describes, Greek travelers and physiologoi (naturalists) from his time had written about fossil sea shells found high on mountains and fish imprints on stone. Theophrastus, his student and protege, describes dug up ivory. Dwarf elephants were among the many remains from the Pleistocene megafaunal fossil beds of Samos, Kos and Tilos islands.

To someone wedded to an unchanging cosmos, this may not have made any difference, Leroi argues.

It would be more than two millennia before Darwin and Wallace put all the pieces together.

Highly Recommended.

Darwin: Househunting In London

via Darwin: The Life Of A Tormented Evolutionist: Adrian Desmond and James Moore

after his engagement to Emma Wedgwood in November 1838..

The couple took the Doctor's advice and opted for a London house until Charles said, 'I have wearied the geological public with my newly acquired cacoethes scribendi [itch to write].' Then they would 'decide, whether the pleasures of retirement & country... are preferable to society'. Charles scouted out houses, traipsing the misty November streets. The West End was out, the traffic noise was deafening (so much so that trials with wood block surfaces were about to start in Oxford Street). Bloomsbury, near the British Museum, was quieter and its leafy squares preferable. Emma gave Charley his marching orders: to investigate 'the back lanes about Regents Park' or nearer to Covent Garden 'if it is not too dear.'  But the astronomic rents came as a shock. The 'landlords are all gone mad. they ask such prices.' L150 a year was nothing. (And Charley remained canny, even with L15,000 in prospect). He and Eras decided that the Bloomsbury squares were the most affordable.

The great man obsessed over mundane matters too after all.

Darwin: Ancestry In Lyell's Pebbles And Herschel's Words

A lovely passage from the 19th century astronomer John Herschel's  letter to geologist Charles Lyell quoted in Darwin: The Life Of A Tormented Evolutionist:

Words are to the Anthropologist what rolled pebbles are to the Geologist- Battered relics of past ages often containing within them indelible records capable of intelligible interpretation- and  when we see what amounts of change 2000 years has been able to produce  in the languages of Greece & Italy or 1000 in those of Germany, France & Spain we naturally begin to ask how long a period must have lapsed since the Chinese, the Hebrew, the Delaware & the Maleass [from Madagascar] had a point in common with the German & Italian & each other. - Time! Time! Time! - we must not impugn Scripture Chronology,but we must interpret it in accordance with whatever shall appear on fair enquiry to be the truth for there cannot be two truths. And really there  is scope enough: for the lives of the Patriarchs may as reasonably be  extended to 5000 or 50000 years apiece as the days of Creation to as many thousand millions of years.

Besides a great age for earth, a notion which was becoming more accepted as geological observations poured in from Britain and other parts of the world,  in the passage are ideas on ancestry and divergence from a common stock. Herschel's musings on language change influenced Darwin. Were these applicable to life too? Darwin on his return from the Beagle voyage in 1836 was engrossed in geological thinking,  hoping to write a book on South American geology. Charles Lyell encouraged him,  and unlike the cantankerous zoology community, he found the geology fraternity more  approachable and gentlemanly. His paper to the Geological Society on the uplift of the Chilean coast was very well received.

But his zoological samples too were being processed by a variety of experts. Richard Owen found out that the large animal bones Darwin had collected were ancient relatives of living South American sloths and armadillos and not related to European and African mammals. There was, Darwin realized, a genealogical succession of fauna which jarred with the commonly held ideas about separate creation of species.  The ornithologist John Gould pointed out that the seemingly disparate collecting of Galapagos Islands ground dwelling birds with distinctive beaks that Darwin had presented to him and thought of as distinct species of finches, wrens and warblers were in fact a closely related group of finches, with more distant relatives found on the South American mainland. And his collection of mockingbirds which unlike  the finches were correctly labelled according to the islands,  turned out to be 3 related species, each distinct to an island... Ancestry and divergence from a common stock..

John Herschel's "mystery of all mysteries" began tempting him. His long association with dissenting intellectuals and radical thinkers who claimed that life should be explainable by natural laws and his own observations of  nature's bounty and variability had made him  receptive to the idea of species transforming into new species. In this, he departed from his geology mentor Charles Lyell who was a scientist molded in the conservative Anglican tradition. Lyell believed that the dynamics of landscapes and the succession of fauna ultimately revealed the hand of a creator. That humans could have originated via transmutation from an ape was anathema to him. For Darwin, such thoughts held no terror.

Geology was to remain an important part of his work life, but in July 1837 he opened and began scribbling ideas in what is one of the most famous scratchpads in the history of science- Notebook B which he titled Zoonomia (after his grandfather Erasmus Darwin's book), marking a decisive shift in emphasis in his thinking from geology to evolution.

Darwin: Encounters In Patagonia and Peru

I'm late by a few days for a Darwin Day 2015 post but wanted to share a couple of passages from Darwin's biography by Adrian Desmond and James Moore which show more facets of his life and personality.

During the survey of Patagonia,  Darwin took to exploring the immense pampas on his  own, hiring guides and horses and living the life  of a gaucho. He was enjoying himself and yet there was an ugly underbelly to this newly constituted society of ranching and exploitation of the great grasslands of Argentina-

Darwin was becoming quite a gaucho himself. The rough-riding suited him perfectly. At night, crouched around a fire, eating roasted game, he jotted down notes and relaxed. "I.. drink my Mattee and smoke my cigar, and then lie down and sleep as comfortably with the Heavens for a Canopy as in a feather bed.' Well  armed, with fresh horses and ruthless companions he had little to fear from the hostiles. Indeed, he was beginning to  appreciate the "great benefits" of General Rosas's war of extermination'. For landowners it promised a bonanza. 'It will open four or 500 miles in length of fine country for the produce of cattle'

Extermination meant the elimination of the native South American population. Darwin did abhor such tactics. He came from an abolitionist background and enslavement and mistreatment of natives affected and disgusted him. Yet, his thinking about the place of natives in human society reflected his own class upbringing. He firmly saw European civilization as superior to other cultures.  He welcomed European settlement of these lands and the conversion of the natives to Christianity. He regarded natives, especially the Fuegians he met in Argentina as a particularly backward and deprived lot. He despaired about the meaning of the variation in human cultures he was witnessing. He hoped that a different upbringing may bring change to the natives and they could learn the ways of the "civilized" world. He turned to the Fuegian natives who had lived in England and spoke English and dressed like Englishman and thought that human behavior is adaptable and plastic. But then he felt his hopes were dashed when these same Fuegian natives reverted to their native ways when brought back to live amongst their people. Darwin then opined that millennia of living amongst harsh environments had led to ingrained habits, deep seated instincts and ways of living  that could not change. Lyell, his geological  mentor had written that humans might be different, but those differences were slight. He was thinking from a creationist point of view, that species were  brought into existence in a moment of creation and varied only slightly. Darwin on the other hand, face to face with the immense cultural differences between native South Americans and Europeans, saw a world of variation. He came close to conflating cultural differences with deep seated biological boundaries.

More that a  year later in July 1835 the HMS Beagle was in Lima, Peru.

There was faded grandeur, but only one thing turned his head. He 'could not keep [his] eyes off the tapadas'- the elegant ladies. Their dress and manners brought out the sailor in him. He felt as though he had fallen amongst 'nice round mermaids'. 

'The ...elastic gown fits the figure closely and obliges the ladies to walk with small steps which they do very elegantly and display very white  silk stockings & very pretty feet.- They wear a black silk veil, which is fixed round the waist behind, is brought over the head, & held by the hands before the face, allowing only one eye to remain uncovered.- But then  that one eye is so black & brilliant & has such powers of motion & expression, that its effect is very powerful'.

But his time Darwin was feeling homesick  too. Ahead lay a long Pacific voyage to Australia and then home via  the Indian Ocean.

His thoughts wandered ...an 'English lady' was someone 'very angelic & good', a type he had 'almost forgotten' about.

Darwin: An Encounter With Beetles

In 1827 Charles Darwin's father Robert Darwin, alarmed that his son was turning into  a wastrel, decided to enroll him at Cambridge with the ultimate  aim of preparing Charles Darwin for a life as a country parson. This would set him up for life among the country gentry he already knew and was comfortable with. Charles's unhappy tryst with medical school in Edinburgh had disappointed his father and the Church of England  seemed a perfect place for a rather aimless son with a love for nature and sport.

"What calling but the highest for those whose sense of calling  was nil?"

Charles Darwin mulled  over his future and was not entirely displeased. Although  he had spent two years in Edinburgh in the company of free thinkers  and religious dissenters who insisted that nature be explained in material terms and not through supernatural explanations, he still, under the considerable  influence of  his  sisters, took  religion seriously. Besides, a career in a rural parish would give him time to pursue his real  passion, which was natural history.

In Cambridge, in the company of  his cousin William Darwin Fox he became obsessed with collecting beetles.

"Nothing was spared in the trophy hunt. He bought a sweeping net and learned how to trap tiny jumping and flying insects. Sheaves if cardboard were festooned with beetles, each pinned in its proper place. He also hired a local to collect the debris from the bottom of barges  that brought reeds from the fens, which he sifted through,  hunting down his prey. It was not simple  slaughter, for some beetles had unexpected defences. One day, on stripping  bark from a dead tree, he  pinned down two rare types,one in each hand. Suddenly, he saw a third new species, too good to lose. His  action was that of a trained egg collector. He popped the right-hand one on his mouth. Unfortunately, it was a bombardier beetle,which promptly lived up to its name by squirting a noxious boiling fluid into his throat, momentarily stunning him. He spat the beetle out, losing it on the ground, and in the confusion dropped the others too". 

It was at Cambridge that Charles Darwin met John Stevens Henslow and Adam Sedgwick. From Henslow he learned botany and the methods of  rigorous scientific observation and analysis. Henslow's recommended books, especially Alexander Von Humboldt's South American travelogue Personal Narrative, inspired Darwin to travel. Henslow  also  introduced Darwin to Adam Sedgwick  from whom he learned the basic principles of geology and formed an appreciation of "deep  time", that the earth must be very old. .."What a capital hand is Sedgewick for drawing large cheques upon the Bank of Time".... This conceptual grounding proved crucial to accommodate his theories of evolution. 

Later, it was Henslow who recommended Darwin's name as a companion to Captain Robert FitzRoy who would be commandeering the HMS Beagle to a voyage of South America and beyond.

..summarized from Darwin:  Life Of A Tormented Evolutionist.

Darwin's Voyage Captured In Sketches And Watercolors

A nice article in the Guardian tells the story of Conrad Martens, an artist who accompanied Darwin for the first few years of his voyage to South America and beyond. Martens sketches and watercolors helped capture not just the lives of local people, landscapes and seascapes but shipboard and other research activity of crew and of Charles Darwin.

Now all this material has been put together in a digital archive accessible via the Cambridge University Library.

 Darwin's Christmas of 1833 with Martens drawing the activities seemed like fun times aboard the Beagle:

“After dining in the Gun-room, the officers & almost every man in the ship went on shore. – The Captain distributed prizes to the best runners, leapers, wrestlers. – These Olympic games were very amusing; it was quite delightful to see with what school-boy eagerness the seamen enjoyed them: old men with long beards & young men without any were playing like so many children. – certainly a much better way of passing Christmas day than the usual one, of every seaman getting as drunk as he possibly can.”

Its a a treat to go online and peruse through one of history's most epic voyages!

...Meanwhile  FINALLY! .. I  am in possession and eager to start Darwin- Life Of  A Tormented Evolutionist by Adrian Desmond and James Moore. I have heard and read so much about the book that I  am now afraid that I might be disappointed. Unlikely, since Darwin's life, work and times are a fascinating topic with many many treasures to mine.

Happy Holidays!

Not Just a Puppet! The Animated Life Of Alfred Russel Wallace

Have you seen this documentary?

The Animated Life Of A.R. Wallace.

Produced by Flora Litchman and Sharon Shattuck and narrated by George Beccaloni of the  Natural History Museum London and Andrew Berry of Harvard University, it celebrates the life and work of Alfred Russell Wallace who along with Charles Darwin discovered the principles of evolution through natural selection in the mid 1800's. Wallace also made pioneering contributions to the field of Biogeography.

A fine example of creative science outreach using paper puppet animation. Beautifully produced and narrated.

Again! Charles Darwin Was Wrong.. About The Tree Of Life

Well.. I guess the headline "Darwin Was Wrong" always sells!

But The Guardian should have thought a little before publishing this. It is an article which appeared sometime back but is the most viewed in the science section and is about how the recognition of lateral gene transfer i.e. the transfer of genes aross taxonomic groups is proving Darwin's idea of a tree of life wrong.

Read this passage:

Evolutionary biologists say crossbreeding between species is far more common than previously thought, making a nonsense of the idea of discrete evolutionary branches.

I don't think their science correspondence Ian Sample thought enough to see the contradiction in this passage.

Cross breeding between species implies that species exist in the first place which in turn means that there has been in existence discrete evolutionary branches i.e. long periods of independent evolution of different populations so as to have accumulated unique features recognizably different from other populations. Its only when there are discrete unique branches is it possible to recognize lateral gene transfer between the two!

For example, coyotes and wolves are closely related animals that occasionally interbreed in the wild. But the fact that we can recognize coyotes from wolves means that these are two discrete lineages having diverged from a common ancestor at some point in the past and have since followed separate evolutionary trajectories accumulating unique traits along the way. Occasional interbreeding between the two does not wipe away all these differences. They remain two distinct branches on the canid family tree.

Gene trees are not the same as species trees. Gene trees reflect the evolutionary history of a gene which may be transferred across taxonomic groups by a variety of processes. Early in the divergent history of populations genes may be exchanged through interbreeding. Or, for example a not so insignificant portion of the genome of mammals is made up of fragments of genes from other species transferred into us long ago by viral infections. However, that does not change the historical fact that the coyote and the wolf, or for that  matter humans and chimps diverged from a common ancestor. Species trees or the tree of life reflects this history of speciation. So, Darwin's tree of life idea is about diverging populations from a common ancestor. These populations despite occasional transfer of genes maintain reproductive integrity and become different enough over time. Life has become diverse over time by such branching. Darwin was not wrong about that.

And what does one make of this confused para- Last year, scientists at the University of Texas at Arlington found a strange chunk of DNA in the genetic make-up of eight animals, including the mouse, rat and the African clawed frog. The same chunk is missing from chickens, elephants and humans, suggesting it must have become wedged into the genomes of some animals by crossbreeding.

Does that mean there was interbreeding between mouse, rats and the African clawed frog? Ridiculous!

Update May 16 2013: There is another potentially misleading passage in the article:

But modern genetics has revealed that representing evolutionary history as a tree is misleading, with scientists saying a more realistic way to represent the origins and inter-relatedness of species would be an impenetrable thicket. Darwin himself also wrote about evolution and ecosystems as a "tangled bank".

Now, the "tangled bank" has nothing to do with lateral gene transfer and interbreeding at all. It should not be conflated with evolutionary relationships being described as a web or a thicket. Darwin was describing the complex inter-dependencies in an ecosystem as organisms compete and co-operate with each other for resources.