India Fossil Outcrops, Horse Domestication, Mars Landscapes

 From the past few days:

1) India is rapidly losing fossil rich outcrops to urbanization, expanding agriculture, mining, and unregulated fossil collection.

On International Fossil Day, October 23, 2021, the Paleontological Society of India, Pune Mumbai Student Chapter, organized a very informative online symposium on this topic. I have linked to part of the talks held that day. Paleontologist Dr. Rajani Panchang was the moderator. Several young researchers describe their field work in Kutch, Tamil Nadu, and Spiti Valley. Over the past several years, changes in land use and unchecked fossil removal has resulted in outcrop degradation and impoverishment.

.Video Permanent Link - India Fossil Outcrops .

Even though the Geological Survey of India and some local agencies have identified locations of geological importance, at present India does not have a law for the preservation of geoheritage sites. D.M. Banerjee writes about the struggle to get the Indian government to take up this issue seriously in his article Fate of Indian Geoheritage and Geopark Bill, published in the July 2021 issue of Current Science.

2) The origin of domestic horses has been a tough case to crack. It was long held using archeological evidence that horses were domesticated by the Botai Culture in Central Asia around 3500 B.C. But ancient DNA studies indicated that these early domesticated lines are not the ancestors of the modern domestic horse. Instead, the origin of the modern domestic horses have been tracked to the Volga-Don region in the Western Eurasian steppes between 2500 and 2000 B.C. The abstract of the paper is worth reading through- 

Domestication of horses fundamentally transformed long-range mobility and warfare. However, modern domesticated breeds do not descend from the earliest domestic horse lineage associated with archaeological evidence of bridling, milking and corralling at Botai, Central Asia around 3500 bc. Other longstanding candidate regions for horse domestication, such as Iberia and Anatolia, have also recently been challenged. Thus, the genetic, geographic and temporal origins of modern domestic horses have remained unknown. Here we pinpoint the Western Eurasian steppes, especially the lower Volga-Don region, as the homeland of modern domestic horses. Furthermore, we map the population changes accompanying domestication from 273 ancient horse genomes. This reveals that modern domestic horses ultimately replaced almost all other local populations as they expanded rapidly across Eurasia from about 2000 bc, synchronously with equestrian material culture, including Sintashta spoke-wheeled chariots. We find that equestrianism involved strong selection for critical locomotor and behavioural adaptations at the GSDMC and ZFPM1 genes. Our results reject the commonly held association between horseback riding and the massive expansion of Yamnaya steppe pastoralists into Europe around 3000 bc driving the spread of Indo-European languages. This contrasts with the scenario in Asia where Indo-Iranian languages, chariots and horses spread together, following the early second millennium bc Sintashta culture.

The paper is open access. And there is an easier to understand article in Nature as well. 

3) The remarkable range of technologies brought to bear on understanding the geology of Mars is giving some spectacular payoffs. Two studies caught my eye:

a) Mars' surface shaped by fast and furious floods from overflowing craters: Lake breach floods produced fast flowing streams that cut deep drainage valleys, reshaping the Mars landscape. Catastrophism has played a large role in the history of Martian surface evolution.

b) The Perseverance Rover rocks on!! The stunning images it has taken of rock outcrops on Mars is enabling geologists to reconstruct details of ancient sedimentary environments. N. Mangold and colleagues describe a delta lake system and flood deposits at Jezero Crater. 

Take a look at the details available to geologists for interpreting sedimentary processes and the rock history.

Source: N. Mangold et.al. 2021:  Perseverance rover reveals an ancient delta-lake system and flood deposits at Jezero crater, Mars.

On Mars, large crater lakes were sites of sediment deposition. Rivers meeting such craters dumped their sediment on the crater floor in lobes that expanded lakewards forming a delta. The architecture of the sedimentary layers within this delta environment has been vividly captured and described in this study. In the image, the bottomset strata are fine grained sediment deposited in waters ahead of the delta. The foreset strata represent deposition on the inclined growing delta front. And the foreset strata are deposits of rivers associated with the delta. The paper is quite detailed and a treat for sedimentologists. But the images can be enjoyed by all. Open Access too!  

Articles: Dehradun, Early Dogs, Warm Blooded Dinos, Louisiana Delta

Sharing some links from the past few days:

1) Dehradun.

A story of the transformation of a beautiful hill town to an ugly unplanned urban center. We shrug resignedly at many such tales from across the country. This one is of Dehradun. Himalaya towns can only be described as disasters in the making. Unscientifically built infrastructure on steep slopes, no garbage management resulting in enormous stray dog and pig populations roaming the streets, and a dwindling water supply. Yet these towns continue to grow, pointing to worsening opportunities for making a livelihood in the Himalayan rural landscapes. The 'smart city' reference is the ultimate insult of all.

Vanishing landscape of ‘smart city’ Dehradun.

2) Early Dogs.

The early stages of dog domestication may have seen a marked behavioral shift appearing before any distinct morphological change. This change in behavior, arising from docile wolves or 'protodogs' living near human camps would have entailed a change in diets.  Scientists have compared wolf and dog like remains from a 28,500 year old site in the Czech Republic. They looked at the dental microwear pattern of these two groups of canids and noticed that the dog like canids show a pattern consistent with eating more hard brittle foods. The wolves show patterns consistent with eating more flesh. 'Throw this dog a bone" wasn't an insult then.

Dental microwear as a behavioral proxy for distinguishing between canids at the Upper Paleolithic (Gravettian) site of Předmostí, Czech Republic

write up: Dog domestication during ice age.

3) Warm Blooded Dinos?

Were Dinosaurs warm blooded like mammals? This debate has raged on for decades. Bone growth patterns have not given any unambiguous evidence of body temperature regulation. A new method known as clumped isotopes may provided a more reliable indicator of estimating body temperatures. Fossilized dinosaur egg shells contain the original calcium carbonate from which these shells were built. A variety of carbon isotopes (C12, C13) may bond with a variety of oxygen isotopes (O16, O17, O18) in the carbonate molecules (CO3). The degree of bonding or clumping of the heavier isotopes i.e. C13 to O18 varies with the temperature during mineral growth. Clumping is more at lower temperatures.

Scientists compared this C13-O18 clumpiness in dinosaur egg shells with C13-O18 clumpiness in the calcium carbonate of mollusc shells from the same fossil bed. Mollusc geochemistry is taken to be a proxy for the ambient conditions. They found out that the egg shells grew at temperatures between 25- 43 deg C, while the molluscs record growth at 25 -30 deg C. This suggests that dinosaurs were capable of maintaining a higher body temperatures than their surroundings.  As a carbonate sedimentologist, I found the details of methods in this paper  of great interest. The researchers used a variety of techniques to make sure that the egg shells had not been altered or subjected to higher temperatures later in their history, which would have made them an unreliable archive of the original temperature during growth. The analyzed egg shells came from Sauropods, Theropods and Ornithischians, a sample across the three main groups of dinosaurs. Very interesting study.

Eggshell geochemistry reveals ancestral metabolic thermoregulation in Dinosauria

write up - Fossil Eggshells Suggest All Dinosaurs May Have Been Warm-Blooded

4)  Eroding Louisiana Coastline.

Over the past several decades, barrages and levees have drastically reduced the amount of sediment that the Mississippi river is carrying to the sea. As a result, the famed Mississippi delta and coastline is eroding away. Efforts are on in a Boston warehouse to figure out a way to reverse this change. An ambitious engineering project which aims at opening up a portion of the levee to funnel sediment into the Barataria Basin south of  New Orleans is being planned. The hope is that the new channel will transport and deposit enough sediment to rebuild part of the endangered delta. A scale model built in a warehouse near Boston is testing the efficacy of this idea.

Fascinating to read the various problems geologists and engineers have to deal with when grappling with modifying nature at this scale.

To Save Louisiana’s Vanishing Coast, Build a Mini Mississippi Near Boston.

Amazonia Before Columbus

This is an interesting article published in the Royal Society's Proceedings B.

During the twentieth century, Amazonia was widely regarded as relatively pristine nature, little impacted by human history. This view remains popular despite mounting evidence of substantial human influence over millennial scales across the region. Here, we review the evidence of an anthropogenic Amazonia in response to claims of sparse populations across broad portions of the region. Amazonia was a major centre of crop domestication, with at least 83 native species containing populations domesticated to some degree. Plant domestication occurs in domesticated landscapes, including highly modified Amazonian dark earths (ADEs) associated with large settled populations and that may cover greater than 0.1% of the region. Populations and food production expanded rapidly within land management systems in the mid-Holocene, and complex societies expanded in resource-rich areas creating domesticated landscapes with profound impacts on local and regional ecology. ADE food production projections support estimates of at least eight million people in 1492. By this time, highly diverse regional systems had developed across Amazonia where subsistence resources were created with plant and landscape domestication, including earthworks. This review argues that the Amazonian anthrome was no less socio-culturally diverse or populous than other tropical forested areas of the world prior to European conquest.

I had read 1491 by Charles Mann so none of this came  as a surprise  to me. I would recommend Mann's book  too.  It is a very well researched richly detailed book on the human landscape of the America's (south and north) before the European conquest. The Amazon basin is covered too and the two things that stuck with me are the "anthrosols" or soils produced or rather enriched in organic matter and nutrients by humans activity like mulching and composting. The map below shows the distribution of these anthropogenic soils.

 Source: Clement C.  et.al. 2015

Their concentrations along the banks of rivers match early European descriptions of farming communities settled along river bluffs, with the interfluvial areas being occupied by semi-nomadic and nomadic hunter gatherers.

The other aspect that fascinated me was the observation of Europeans of the incredibly varied fruit trees from the Amazon jungles. Many true wild fruit are generally small, sour, bitter, thorny, spiky. The native people over millennia had transformed them by selective breeding into the edible fruit smorgasbord that one sees today. Imagine large areas of "virgin" Amazon forests were actually abandoned fruit orchards!

Read this article though.

Scientists At Work- The Latest On Dog Domestication

Over at Science Magazine David Grimm has written a very informative article on the status of research on dog domestication. Its about the techniques being brought to bear on the question of the place and timing of dog origins and also about the scientists involved in the research, their pet theories and the conflicts within the field.

An excerpt:

Hulme-Beaman has spent the past 6 months traveling the world in search of ancient dog bones like this one. He's found plenty in this Ohio State University archaeology laboratory. Amid boxes stacked high with Native American artifacts, rows of plastic containers filled with primate teeth, and a hodgepodge of microscopes, calipers, and research papers, a few shoe and cigar boxes hold the jigsaw pieces of a dozen canines: skulls, femurs, mandibles, and vertebrae.

It's all a bit of a jumble, which seems appropriate for a field that's a bit of a mess itself. Dogs were the very first thing humans domesticated—before any plant, before any other animal. Yet despite decades of study, researchers are still fighting over where and when wolves became humans' loyal companions. “It's very competitive and contentious,” says Jean-Denis Vigne, a zooarchaeologist at the National Museum of Natural History in Paris, who notes that dogs could shed light on human prehistory and the very nature of domestication. “It's an animal so deeply and strongly connected to our history that everyone wants to know.”

And soon everyone just might. In an unprecedented truce brokered by two scientists from outside the dog wars, the various factions have started working together. With the help of Hulme-Beaman and others, they're sharing samples, analyzing thousands of bones, and trying to set aside years of bad blood and bruised egos. If the effort succeeds, the former competitors will uncover the history of man's oldest friend—and solve one of the greatest mysteries of domestication.

The main points of contention:

a) did dogs originate in China around 15,000 years ago? this is based on the greater genetic diversity of East Asian breeds suggesting earlier origins than elsewhere, a notion that is opposed by some who say that diversity could reflect later migration.

b) did dogs originate in Europe/ West Asia? between 19,000 and 32,000 years ..  this is based on DNA comparisons of ancient and modern dogs and wolves from Europa and the America's which suggest that modern dogs are most similar to a now extinct population of wolves from Europe. This finding is criticized for its lack of samples of ancient dogs from China (there aren't any found as of yet) and for possible confusion in identifying ancients wolf  from ancient dog remains.

c) do unusual skeletons having wolf/dog mixed features as old as 30,000 from Belgium and Siberia represent ancestors of living dogs or extinct populations indicating failed attempts at domestication? ...  do these samples represent dogs at all or are they just strange looking wolves... a question that is now  being probed  used computer assisted morphological analysis.

there is plenty of think about..  read the full article here.

Dog Domestication Controversy: When, Where And How Many Times?

Interesting article in Nature on advances in our understanding about dog domestication. Apparently it is a "sexy field" of study:

"In recent months, three international teams have published papers comparing the genomes of dogs and wolves. On some matters — such as the types of genetic changes that make the two differ — the researchers are more or less in agreement. Yet the teams have all arrived at wildly different conclusions about the timing, location and basis for the reinvention of ferocious wolves as placid pooches. “It’s a sexy field,” says Greger Larson, an archaeogeneticist at the University of Durham, UK. He has won a £950,000 (US$1.5-million) grant to study dog domestication starting in October. “You’ve got a lot of big personalities, a lot of money, and people who want to get their Nature paper first.”

Fossils and genetic data are in conflict too. Fossil skulls with dog like features dating back to around 33,000 years have been reported from Siberia and Belgium. There is genetic work that suggests that China was where the first dogs were domesticated at a similar early date of around 32,000 years ago. Other scientists feel that these early lineages went extinct without contributing to extant dogs which according to them evolved post ice age maxima beginning around 15,000 years ago or so. Yet others think that dog domestication coincided with the advent of agriculture about 10,000 years ago.

I think multiple episodes of domestication at various times is an entirely reasonable possibility given that both wolves and humans are hyper social and the opportunities to clash, cooperate and be fascinated with each other would have arisen again and again.

Expect more trading of intellectual blows as genomics will bring a tighter focus on the timing and geography of dog origins.

"The move to look at ancient DNA could make the small field of dog genetics even pricklier, because archaeological bone samples are so precious. Novembre says that he finds the field more fractious than human genetics, and says that his experience has given him pause about future canine work. “It’s really intense in the dog world,” he says. But Boyko, who also collaborates with the Chinese group, says that although the field is competitive, it remains collegial. “At the end of the day, we sit back and enjoy a beer together when we see each other.”

Out Of Siberia - Dogs Not Humans

The endearingly fascinating topic of dog domestication is in the news again. A skull with features that are a mix of wolf and dog was found in the Altai mountains of Siberia. It has been dated to around 33,000 years ago, before the Last Glacial Maximum, a period of intense expansion of polar and mountain ice sheets that began around 26,000 years ago and lasted until around 19,000 years ago.  It may represent an early wolf to dog domestication "in progress", but one that researchers feel was aborted by the advent of the last Glacial Maximum, when human populations in this region dispersed.  There is no evidence in younger deposits from this area of domesticated dogs, despite there being an occasional human presence.

I wrote about this topic some weeks ago and I commented that there probably were many such instances of marginal members of wolf packs getting acculturated to humans and getting self-domesticated or being pushed in that direction by human selection of docile traits. This is after all a meeting between two hyper-social species and contact between wolf and humans would have been a very common occurrence. Another equally old dog skull from a cave in Belgium suggests that there were multiple instances of dog domestication.

What struck me about this latest discovery is the age and the place - 33,000 years ago in the Altai region...... Denisovans??

Modern humans were not the only inhabitants of this region of Siberia.  A  population of another distinct human "species" or variety, descendants of an earlier human migration from Africa about half a million years ago, also lived in this region. Their remains  were found near Denisova cave in the Altai mountains of Siberia and judged to about 41,000 years old.

Its fascinating to speculate on whether there were any instances of wolf domestication in the company of these other human species. The Denisovans  (and the Neanderthals) were human lineages that had a long presence lasting more than one hundred thousand years in Asia and Europe and they would have encountered wolves routinely. We don't know anything about the social and cultural aspects of Denisovan society, but we do know that their cousins the Neanderthals lived in closely knit social groups.

A lot has been said about what the differences may have been between these archaic human groups and "modern" humans. Put forward are differences in cognition (we were just smarter), language and communication skills, division of labor (modern humans had more efficient food gathering strategies),  home range and mobility affecting trade and cooperation with other groups (Neanderthals did not trade as much with other groups). These are all speculative and maybe we can add one more.

These archaic humans did not or were unable to domesticate the wolf. No remains of domestication have been found so far, associated with the Neanderthals. Does the same apply to the Denisovans and other archaic human groups scattered across Africa and Asia?

That off course could be a reflection of something about their behavior as individuals and as a society. Perhaps the wolves themselves stayed away sensing a lack of that bit of empathy, perhaps their hunting methods did not require cooperation with a willing canine partner. If there is evidence for dog domestication or partial domestication about 33,000 years ago, could there be even earlier instances of the dog? And if the timing of dog domestication overlapped with modern human contact with Neanderthals and Denisovans from 45,000 to 30,000 years ago,  did the dog give some advantage to modern humans in eking out a living over these other human "species"?

Some Thoughts On The Evolution Of Dogs

Let me begin though with David W. Anthony's musings about the domestication of horses from his book The Horse The Wheel And Language:

Modern horses are derived from very few original wild males, and many, varied females.

In wild horse society there is a female hierarchy and mares are disposed to follow the lead of a dominant mare. Stallions on the other hand are more independent and react violently when confronted.

...A relatively docile and controllable mare could be found at the bottom of the pecking order in many wild horse bands, but a relatively docile and controllable stallion was an unusual individual - and one that had little hope of reproducing in the wild. Horse domestication might have depended on a lucky coincidence: the appearance of a relatively manageable and docile male in a place where humans could use him as the breeder of a domesticated bloodline.

From the horses perspective, humans were the only way he could get a girl. From the human's perspective, he was the only sire they wanted.

Well said!

Horse domestication depended on active selection of traits by humans from the very start. It may have been different for dogs at least in the earliest stages of human wolf interaction suggests naturalist  Mark Derr in an interview on Fresh Air. 

There are many hypothesis on how wolves got domesticated into dogs.

The puppy hypothesis suggests that abandoned wolf puppies were adopted by humans and then the more sociable and docile amongst them were allowed to breed. This involves selection pressures imposed by humans from the very start.

Then there is the garbage midden hypothesis. Wolves started hanging around human camp rubbish sites.  The key element in this hypothesis is that only wolves who were instinctively docile and perhaps not getting enough food in the wild engaged in this behavior. So there was a self selection for docile traits in the wolves who gradually got used to be near humans.

The third is the hunting band hypothesis. Humans began following wolves on hunts or maybe wolves started following humans on hunts.  These bands of wolves became socialized with humans and  isolated from other bands of wolves. Again it is possible that instinctively docile wolves were more likely to follow human hunts if the reward at the end was food which was hard to obtain otherwise. So there is an element of self selection in this hypothesis as well.

Mark Derr tilts towards this third hypothesis. To me, it hard to pick out the stronger contender. The three hypothesis are not mutually exclusive. The thing is that all three situations would have been a common occurrence. For example its reasonable to imagine a scenario whereby a docile male sifting through the garbage dump gets bold enough to latch on to a female adopted as a puppy and living amongst humans.

The three situations would have overlapped many times. Socialization could have occurred via all these three interactions. After that there would have been more severe direct intervention and selection by humans for traits like docility.

There are other interesting questions about dog domestication. For example, was there just one center of domestication or did domestication take place many times in different places? The Middle East is considered the likely place for dog domestication based on  arguments that the dogs from this region show more genetic variation pointing to a source population of greater antiquity. There also have been a case put forward for China being the place where dogs were first domesticated.

Considering the likelihood of repeated contact between wolves and humans there were probably many independent attempts to domesticate the wolf. Fossils of dogs and wolf-dog hybrids as old as 30 thousand years ago have been discovered from various place in the Middle East, Europe and Siberia suggesting multiple domestication attempts, perhaps successful ones.

What comes to my mind is how incredibly violent the initial process of domestication would have been. Wolf-dog pups and young adults not to the liking of humans in terms of their temperament and behavior and form would have been put to death often by a whack to the head.

As a dog lover I shudder at the thought.

Reassembling Pangaea In The Year 1493

This is the second great talk I have heard on Fresh Air in the past few days. Author of the book 1493: Uncovering the World Columbus Created Charles Mann talks about the impact on the Americas and Europe due to the sudden exchange of humans, animals, plants, parasites between the continents following Christopher Columbus's voyage to the America's in 1492.

He frames this exchange within a larger geological context -

Mr. CHARLES MANN (Author, "1493: Uncovering the New World Columbus Created"): Well, if you think about it, you know, there's been a tendency in textbooks now to kind of downplay Columbus because they say he was a bad guy, and he mistreated Indians, and he discovered the Americas by accident and so forth.

But to ecologists, he was this super-important figure, and the reason is that 200 million years ago, as you remember learning in school, the world was a single, giant land mass they call Pangaea, and geological forces broke it up, creating the continents we know today. And over time, they developed completely different suites of plants and animals.

And what Columbus did was bring the continents back together. He recreated Pangaea, in effect, and as a result, huge numbers and plants and animals from over there came over here, and huge numbers of plants and animals from over here came over there, and there was a tremendous ecological convulsion, the greatest event in the history of life since the death of the dinosaurs.

As an aside.. he is right off course that after the supercontinent Pangaea broke up more than 200 million years ago, different continents had evolved different suites of plants and animals. But Europe, Asia and the America's were not completely isolated from each other from the breakup of Pangaea until the Columbian exchange. From time to time during the early Cenozoic there were faunal exchanges ..mammals especially migrating via the Beringia land bridge (Siberia -Alsaka) to and from between Asia and America and via the Greenland land bridge in the early Cenozoic between Europe and America. These immigrants also must have caused ecological upheavals of their own. They would have been competition for resources and they must have brought over parasites and caused much death and destruction. We have a more guilt free dispassionate view of these faunal turnovers and extinctions. Tim Flannery has the details of these ancient exchanges that took place tens of millions of years ago and the ecological history of the America's in his excellent book The Eternal Frontier.

Charles Mann though weaves many fascinating stories of the Columbian exchange. One that caught my eye was on the impact of malaria on the institution of slavery. The climate which made the southern parts of the America's friendlier to intense plantation agriculture were also environs in which malaria thrived. Africans were more resistant to this newly introduced disease while indentured servants from Britain and Europe who were more commonly hired to work the fields in the earliest days of colonial settlement were dying off in great numbers. It made economic sense to start bringing over more Africans to work on the plantations.

The word exchange means that the movement of people, animals, plants and diseases went both ways. The damage in terms of human deaths, deprivation and societal disruption though was overwhelmingly more in the America's. I have often come across a common impression that it was technology, firepower and political and financial institutions that gave Europeans the decisive advantage over Native Americans. Those did play a role, but the factor that titled events in favor of Europeans was the evolutionary history of peoples, rather resistance or lack thereof to disease. In a strange twist of fate, Europeans benefited from both a lack of resistance to certain diseases as well as from resistance to others. A lack of resistance to malaria stopped newly arriving European poorer classes from being tied to harsh servitude in plantations in the south where malaria was prevalent. Instead resistance to malaria lead Africans into bondage. On the other hand Europeans had evolved immunity against small pox and many infectious diseases contracted from domesticated animals from time to time. Native Americans had not encountered small pox before and not having a history of animal domestication lacked immunity against animal diseases that occasional jumped hosts. They died in their millions leaving vast swathes of countryside unattended and empty for European settlers.

America though had its grotesque revenge via the potato and guano which was used as a fertilizer. Originating in Peru, the two teamed up and initiated intense potato cultivation all across Europe. Ireland especially became addicted to the potato. But the spud carried with it a fungal parasite. In the mid 1800's the potato crop all over Europe failed. More that a million Irish died of starvation partly due to the blight and partly due to Britain's refusal to divert grain to Ireland.

One last fascinating demographic titbit about the role of Africans in building North America:

..And the second thing is that what happened after the Europeans came was not so much that Europeans came, but the Africans came. The number of Africans who came to the Americas up till about 1840, 1850 far outweighed the number of Europeans. There were three Africans for every European who came to the Americas in those first couple hundred years.

GROSS: And this is because of slavery.

Mr. MANN: Because of slavery. And so the Europeans who came, like, you know, many of my ancestors in the later part of the 19th century came to landscapes that had been radically changed, but they had - and to new cities. But those cities had been built (by) African hands, the landscapes had been reworked by African hands, the boats that were going up and down the rivers were piloted by African crews. And so that - there was a tremendous change in the very distribution of the human race on the planet as a result of Columbus.

Globalization has done great things to us as a people, but it has been served up with more than its fair share of pain.

Listen / Transcript

Self Domestication Of Humans And Symbolic Language

There are topics I like to read about and I think I am understanding the subject matter as I read along. But if asked to explain that to someone else.. I would probably draw a blank.

The evolution of language is a fascinating topic and on NPR's Cosmos and Culture blog language experts Terrence Deacon and Ursula Goodenough write a post on the evolution of symbolic language in humans:

The world of symbols is an artificial niche, its ecology radically different from the biological niche we also occupy. In the same way that beaver dam-building has created an aquatic niche to which beaver bodies and behavior have adapted over their evolutionary history, our cognitive capacities have adapted to our self-constructed symbolic niche.

..and this very interesting take on how domestication or rather establishment of a particular social and cultural niche in early human societies may have prodded the evolution of complex language:

Recent investigations of birdsong offer some clues in thinking about language evolution.

As expanded in an earlier blog, a comparative study of a recently domesticated bird and its feral cousin revealed that the domesticated lineage is a far more facile song-learner, with a much more complex and flexible song, despite the fact that the domesticated bird was bred for plumage coloration, not singing.

That this behavioral and neural complexity arose spontaneously was surprising given the common assumption that song complexity evolves under the influence of intense sexual selection, which was not operant under the breeding regime. One intriguing interpretation is that the relaxation of natural and sexual selection on singing was in fact responsible for its complexification. With song becoming irrelevant to species identification, territorial defense, mate attraction, predator avoidance, and so on, degrading mutations and existing deleterious alleles affecting the specification of the stereotypic song would not have been weeded out, the result being a reduction in the innate biases controlling song production. With specification of song structure no longer strictly controlled by the primary forebrain motor center, auditory experience, social context, learning biases, and attentional factors could all begin to influence singing, the result being that the domestic song became more variable, more complicated, and more influenced by social experience.

Relaxation of selection may have led to phenotypic plasticity - in this case an increased repertoire of behavioral /audio responses - being tolerated and eventually the genetic basis for this increased range was positively selected for over evolutionary time and became an adaptive feature.  I think this is called genetic assimilation or the Waddington effect.

I may be wrong about this being an example of genetic assimilation... but...in any case the article is worth reading.

I Hereby Bequeath You My Dog

Nicholas Wade writes about the possible locale of the earliest dog domestication and its impact on human societies:

Dog domestication and human settlement occurred at the same time, some 15,000 years ago, raising the possibility that dogs may have had a complex impact on the structure of human society. Dogs could have been the sentries that let hunter gatherers settle without fear of surprise attack. They may also have been the first major item of inherited wealth, preceding cattle, and so could have laid the foundations for the gradations of wealth and social hierarchy that differentiated settled groups from the egalitarianism of their hunter-gatherer predecessors. Notions of inheritance and ownership, Dr. Driscoll said, may have been prompted by the first dogs to permeate human society, laying an unexpected track from wolf to wealth.

Figure below (see link for explanation) depicts the genetic relationships between dog breeds to wolves.

Close proximity to animals and its impact on both biological and cultural evolution of humans is increasingly being appreciated and studied. In a sense domestication goes both ways...e.g. was inter-tribe /clan/family violence moderated by the presence of dogs protecting settlements?

Here is a link to the paper in Nature and if you want to listen to one of the lead scientists Robert K. Wayne I dug out this old talk on NPR on dog evolution and domestication. Its worth a listen.