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Updated: March 25, 2010 02:06 IST

How climate influenced the evolution of humans

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A Hoolock Gibbon at the Gibbon Wild Life Sanctuary in Jorhat district of Assam. Photo: Ritu Raj Konwar
The Hindu
A Hoolock Gibbon at the Gibbon Wild Life Sanctuary in Jorhat district of Assam. Photo: Ritu Raj Konwar

A poem by Sant Kabir Das goes thus:

Maati kahe kumharse, tu kya rhondhe mohay,

ik din aisa aayega ki main rhondhoongi tohay

(Clay tells the potter: you are moulding me now; a day will come when I shall mould you. — A poem by Sant Kabir Das).

Kabir could just as well have used the past tense! Long long before the potter came on earth, there was clay. Indeed, clay- symbolic of changing conditions on earth and its climate- sculpted the potter in the first place.

As pointed out in the previous column on March 11th, it is on this grand theme of understanding climate's influence on human evolution that a group of Academies in the US are proposing a long-range research programmes (see their paper at focus will be on two broad themes. The first is on impacts of climate change and climate variability on human evolution and dispersal. It is now realized that the build up of oxygen, through billions of years of photosynthesis by plants, led to a major shift around 500 million years (MYr) ago, in the atmosphere, environmental ecology and landscape development. This, in turn, is thought to have led to an “explosion” of life forms.

On the flip side, a massive meteoric crash on earth 65 Myr ago led to not only the extinction of dinosaurs, but of many other species through the crash, the resultant heat and the cutting off of sunlight through the massive dust clouds and the resultant cooling of the earth's surface.

Not all climatic changes need be so drastic. Large scale changes in climate tend to change the landscape ecology. This in turn affects life forms.

Some of them cope with it and survive while others lose the battle. This in turn leads to genetic selection and variation – natural selection and survival of the fittest.

Fossil, climate data

Research here wishes to collect as much fossil data and climate data from across the world, particularly pertaining to the last 8 Myr, the period when the primates emerged. Also high-precision records of climate changes close to the sites where they lived and bred would be needed. These records can be obtained by deep drilling of lake and ocean beds and analyzing them much the way climate changes are read based on studying tree rings.

But in order to do so, we need new tools which reliably reconstruct past environmental conditions.

In a sense this is similar to what the biologists had waited for when they wanted to read the human genome: the development of high speed robotic DNA sequencing machines on one hand, and of complex computer algorithms and networking to make sense out of the data on the other. Clearly then, this theme of determining the changes in climate and environment that occurred 8 Myrs ago, 2 Myrs ago (when humans arrived on earth), and 200,000 Yrs ago (when we began moving out of Africa) needs new approaches, tools, funds and international collaboration (much as the human genome project did).

Theme II of the effort asks the following. What are the physical and biological mechanisms whereby past changes in the environment may have produced evolutionary and behavioural responses in the great apes and in humans? The effort here will have to be more region-specific. What were the climatic patterns in Africa, West Asia and Eurasia? And how can one connect these with archaeological and DNA data available from fossils of apes and humans?

Collaborations needed

How can we do so? This would require collaboration between oceanographers and geologists who have put together models of oceans and coast lines, volcanic eruptions and climatic variations over long periods in earth history on one hand, and anthropologists and paleontologists, who have been gathering data on vegetation, animal and human fossils on the other.

It would further need gene biologists who can study the variations in whatever DNA samples they can lay these hands on, and reconstruct our genetic history.

The Academies, in short, envision a new scientific program for international climate and human evolution studies.

This program would consist of (a) a major exploration to locate new fossil sites, (b) a comprehensive, integrated program of drilling lakes, lake beds and ocean basins surrounding the regions where the great apes and early humans lived; these will have to be of sufficient high resolution so that short-term events can be described, and (c) a major set of climate modeling experiments which could provide data on key time periods and regions that are critical for understanding human evolution.

With such a grand international effort, it should be possible to describe how and when did evolutionary changes occur as the great apes gave rise to humans.

And with high power DNA sequencing methods, we can sample Homo sapiensand other mammals from all parts of Africa, so as to compare genetic changes with climate changes over the last 200,000 years.

It should also be possible to estimate the size of the population during this period, using population genetics parameters.

All this would require an international collaborative program, similar to the International Panel on Climate Change (IPCC), or the UN bodies, with participation from as many countries as possible and funding from public and private sources. And it should engage the lay public, since we are always fascinated by our own history.

India's rich tradition

India has a rich tradition in researchers in archaeology, paleobotony, genetics, and ocean science. We must join this forthcoming international program, by providing talent and treasury.

We often pride ourselves on our ancient heritage.

Let us put our efforts into understanding our evolutionary heritage, since we often repeat the platitude ‘Vasudhaiva kutumbakam' (the whole world is one family). Also, The program attempts to understand how clay moulded us into existence in the first place.

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