Sunday, January 27, 2008

Human evolution, fire, and food

From meat eating to cooking - the key to our minds?

What made us human? This age old question has been one of the foundational underlying motives –a holy grail- for generations of anthropologists through the ages. As the accumulating body of knowledge regarding our origins continues to grow and coalesce, a dim image of our evolutionary past is finally beginning to take on a recognizable shape.

One of the more interesting details among the blank pages of this incredible although incomplete body of knowledge is- what could have triggered the progression of an ancient hominid ancestor and prod it to follow a path that eventually led to “us”.

Indeed, this conundrum preoccupies more than just a few professional anthropologists in a grand quest for understanding. It has become apparent that an innumerable quantity of events- some major, others almost inconsequential- have contributed to the type of hominid we are today. It is highly likely this unique history will not repeat itself ever again in exactly same way even if a similar story unfolded somewhere else on another planet- or here in another time.

Peering far into the distant and foggy details of our past Richard Wrangham; professor of Biology and Anthropology at Harvard University, has pondered these fascinating issues searching for plausible key events that may have stoked the fire of evolution towards our state of being today. The improving anthropological data base and keen insight has allowed Wrangham to perhaps come upon what may be one of the very keys to our relatively short lived existence.

The rapid development of our brain size seems to be intimately intertwined with different developments in our history that created an interdependent chain of events that basically fed off of each other. The move to bipedalism may have allowed various advantages for certain primate ancestors to adaptively radiate into new and changing environments. A few of these lineages may have survived and developed certain social and technological advances allowing further opportunity to expand. Alas, of these it seems almost none survived the ruthless demands of nature except perhaps a few primate-like lineages.

At a time somewhere around 2.6 million years ago among these hominid creatures –pre-human bipeds- there appeared a fossil species names Homo habilis that according to Wrangham “…tell of incipient humanity, but…their chimpanzee-sized bodies, long arms, big guts and jutting faces made them ape-like.” It seems the anthropolic record shows that it is this hominid lineage that stumbled upon a new and heretofore unprecedented source of food (at least consistently)-meat eating. Though a huge milestone towards the eventual emergence of our own kind, it may not have been key we thought it was to the type of brain expansion that followed.

A million years would follow before the human like Homo erectus appears on the scene. These hominids differ from habilis and closely resembled our own species. Wranghem notes “Their brains were bigger than those of habilis, and they walked and ran as fluently as we do…To judge from the reduced flaring of their rib cage they had lost the capacious guts that allow great apes and habilis to eat large volumes of plant food. Equally strange for a “helpless and defenseless” species they had also lost their climbing ability, forcing them to sleep on the ground- a surprising commitment in a continent full of big cats, sabretooths, hyenas, rhinos, and elephants.”

Wringham realized these peculiar findings could be a telltale sign of one of those key milestones that accelerated evolutionary brain expansion in hominids. It had been believed that meat eating was one of these fulcrum moments- but as we noted- the improving fossil record has pre-human hominids such as H. habilis meat eating well before truly human like qualities began to emerge as in H. erectus. While meat eating was a crucial development, what other condition could have occurred during this period that finally put one habilis group firmly on the road to humanity?

Here Wringham posits a truly fascinating possibility, one that rings true and threads nicely into the tapestry of how we came to be from them. He suggests that it was the control of fire and the ingestion of cooked food that changed everything. In spite of the fact fire use becomes spottier the farther back in the historical record you go, Wringham maintains that this clutch tool could have triggered the cascade. In fact, it is interesting to note that evidence for the use of fire –spotty though it may be- goes as far back as 1.6 millions years to about the time H.erectus appeared.

Based on this “epiphany” Wringham came to some realizations that indeed have solid merit. He claims that “humans are biologically adapted to eating cooked diets, and the signs of this adaptation start with Homo erectus. Cooked food is the signature feature of the human diet. It not only makes our food safe and easy to eat, but it also grants us large amounts of energy compared to a raw diet obviating the need to ingest big meals. Cooking softens food too, thereby making eating so speedy that as eaters of cooked food, we are granted many extra hours of free time every day.” This situation may have been a key catalyst for the subsequent exponential expansion of technological and socio-cultural development.

This fascinating theory offers a window into a critical period of human evolution that opened the doors to the emergence of H. sapiens. As we expand our understanding of human origins, it is becoming abundantly clear just how mundane we truly are- that we are just another animal driven completely by the rule of evolution and the whims of happenstance. Our “unique and special” mental capacity is really just another reflection -among many- of nature’s possibilities


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