Beyond Stones and Bones

The article “Beyond Stones and bones” by Sharon Begley introduces us to the world of science of brain and DNA that is redefining the way we look at the human evolution. It gives us a clear picture of how technology rather than rocks and bones have helped our archeologists to discover n number of new dimensions of the history of the most advanced creature on earth called Human Beings. It was Mark StoneKing who first thought of comparing DNAs of head lice and body lice to calculate the first time body lice came to the scene.

This revolutionary technique, when applied, has changed the long established belief that human evolution was a single-file parade. Instead the author and scientists now suggests that it had many files or branches which met a dead end somewhere eventually. This has been supported by the fact that DNA analysis of Human DNA and chimp DNA which differs by just 1. 2 percent has concluded that the lineage split of humans and chimps occurred 5-6 millions back, that is, human-like features in human started developing 5-6 millions back.

At the same time, scientists have unearthed Sahelanthropus tchadensis (nicknamed Toumai), the oldest available fossil of humans, which has very visible human-like features but existed 7 million years earlier. This clearly suggests that Human evolution was not a “begat” model where Toumai begat Australopithecus who begat Homo habilis who begat Homo erectus who begat Homo sapiens. The million-dollar question now that pops up is then how did the change come and how did we evolve to what we are now.

Sharon briefs the reader on the recent discovery of a gene called HARI (for human accelerated region) that answers the question to a large extent. Research shows only 2 of its 118 million chemical “letters” have changed since the last 310 million years but an amazing 18 letters changed in a flash since the split of lineage 5-6 million years back! That’s when, scientists say, the present line of ancestors started evolving. This study combined with the study of host of other genes like PDYN effectively also advocates that man was the “Hunted” rather than the “hunter”.

This has, in addition, been supported by fossil evidence that showed holes in the skulls unearthed that is attributed to the attacks of big cats. Then how did our ancestors survive in a world of predators? The has been answered by Sussman who hints that it was then that social skills among humans developed and it is this trait that helped them survive. This has been supported by both genetics and, paleoneurology that describes the role of Oxytoxin in human social skills. The Y chromosome, however, has a different story to tell.

According to Peter Underhill who is researching this aspect, the most recent common ancestor of all men alive today lived 89,000 years ago in Africa. The first brave modern humans—and therefore, unlike the earlier wave of Homo erectus into Asia a million years ago, the ancestors of everyone today—departed Africa about 66,000 years ago. We are their descendants. Finally the rapid structural changes in humans from then on (66,000 years ago) have found reason and evidence from three genes that the scientists discovered recently: The first, called FOXP2, plays a role in human speech and language.

Scientists trace back its effect to less than 200,000 years ago—about when anatomically modern humans stepped onto the world stage—and maybe as recently as 50,000. Another interesting gene is the microcephalin, which affects brain size. It is believed to have started playing its part around 37,000 years back when symbolic thinking developed in our ancestors. And the third gene, ASPM, evolved in 5800 years ago when the first cities on this planet were built. This suggests that we are still evolving!

To conclude, the article gave brief yet comprehensive insight to the role the advancements in technologies that include the science of brain and DNA play in our quest for our ancestors. The important finding that discredits the theory of single-file evolution is a major contribution of this development. However, it is not to conclude that fossils have become a passe. Instead they have become all the important to this study as now they serve as the beacons that would eventually take us to the cradle where human evolution took birth.