Readings: Earth's Ice, Neanderthal Women, Indian Monsoons

Some good stuff from the past few weeks.

1) How much of the Earth's Ice is Melting? Sid Perkins writes about the variety of methods of estimating ice loss from the high latitudes. These methods are showing where and how much melting is taking place, in turn, helping scientists make predictions of future sea level rise. The overall scenario is rather gloomy. 

2) The Lives of Neanderthal Women. "Archaeology is no exception to biases against women’s interests across science and the humanities". Archaeologist Rebecca Wragg Skykes expertly constructs a picture of what the lives of Neanderthal women might have been like.

3) Indian Monsoon Across Millennia. Stalagmites from a cave in Meghalaya, NE India are giving paleoclimatologists information about monsoon variability over a thousand years. Their geochemistry points to periodic deadly droughts that coincide with phases of major social and political turmoil in India. Paper authors Gayatri Kathayat and Ashish Sinha describe their research. 

 

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.

Male Australopithecines Were Not House Husbands

Evolution research is routinely misreported in the Indian media and I had a chuckle when I read this summary published in the Times of India:

Early women worked, men stayed home:

Early species of cavemen who roamed the earth two million years ago did not go to work but stayed at home and looked after the kids, while their females earned bread for the family, says a new research.

Scientists at the University of Oxford arrived at the conclusion by using new techniques to extract information from the fossilized teeth of our ancient human ancestors.  

No..no...  the conclusion scientists reached after studying strontium isotope content of fossilized teeth from two species of ancient hominins from South Africa was not about the daily division of labor between the sexes but about another aspect of their social life.

Different rock types like granites, basalts, dolomites have characteristic strontium isotope signatures. Plants take up strontium from bedrock and derived soil. Animals eat those plants and the strontium ends up in the enamel of their teeth. Analyzing the strontium isotope values of ancient mineralized teeth can help identify the geological substrate on which ancient animals, in this case ancient hominins lived. 

Scientists tested 19 teeth from the Sterkfontein and Swartkrans cave sites in South Africa dating from about 2.4 to 1.7 million years ago from two hominin species, Australopithecus africanus and Paranthropus robustus. These samples were preserved in a dolomite substrate.

The fragmentary body fossil record of these two species hints at a considerable degree of sexual dimorphism i.e. the females were significantly smaller in size than the males. When the the teeth were analyzed scientists found that a large proportion of smaller teeth likely belonging to females show strontium isotope values not reflecting the local landscape i.e. not reflecting the dolomite substrate, suggesting that many females had come into this area from outside the geological terrain where these sampled populations lived. On the other hand,  a large proportion of teeth likely belonging to males reflected local geology.

So, the inferences drawn from the strontium isotope values were (a) in these ancient hominins, females on reaching maturity dispersed away from their natal or family group and joined another group while males remained with their group and did not migrate elsewhere, and (b) male hominins had small home ranges i.e. they stayed most of their lives in a relatively small area.

Many social animals show a pattern of either the females or males leaving their family group on maturity, a behavior that may have evolved to minimize inbreeding. The social pattern of female dispersal inferred in these ancient hominins is similar to that seen in chimpanzees and many modern human societies as well.

Social behavior does not fossilize. Tools made by ancient humans is one way to understand certain aspects of behavior. In this case the scientists linked a physiological mechanism - the uptake through food and localization of strontium in teeth - to social behavior.

I thought it is a smart piece of forensic science.. even though it didn't tell us whether or not those ancient males were house husbands!

Science Daily summary.