Published: February 26, 2009 10:20 pm      

Of lice and men: How we track our ancestors

Big steps in human prehistory

With the decoding of the human genome in 2003, scientists are now using special genetic analysis to determine the approximate times of key events and developments in human prehistory (prior to 3,000 BCE).

Earlier, anthropologists were limited to analyzing tools, carbon dating cloth and charcoal remnants from fires and temperature records from ice cores and the soil. There were more questions than findings.

But now a concerted effort by many kinds of specialists including population geneticists, social anthropologists, evolutionary psychologists, evolutionary anthropologists and evolutionary biologists has led to some intriguing preliminary results.

These are described in Nicholas Wade’s “Before the Dawn: Recovering the Lost History of Our Ancestors”, a Penguin Book (2006). Wade is a reporter at the New York Times, previously working for Nature and Science and the author of five previous books. Following is a brief description (in time order) of the crucial events in our species’ story.

1.7 Million years ago saw the appearance of Homo Ergaster, the first primate to show most of the skeletal features that we have. Ergaster had arm length like ours, suggesting that they were not swinging from trees but walking along the ground. Ergaster’s smaller stomach indicates a meat rich diet and likely tubers.

This species utilized a much better array of tools than previous species. Ergaster was the first Homo species to have a nose. Paleoanthropologist Richard Klein also suggests that Ergaster shed its hair, as a better way to cool its body and brain in the heat of the savanna where it lived. Without heavy hair, it was easier to check for parasites and thus make a better choice for a mate.

The lack of hair would have led to a darkening of the skin through mutation of the melanocortin receptor gene. This conversion to dark skin color would have taken place about 1.2 million years ago in the African savannas. With these changes, some of these early Homo left Africa, first reaching Asia at least a million years ago and Europe a half million years ago. Then 200,000 years ago, our African ancestors developed brains of the same volume as our own (1,200 cubic centimeters).

A big change 72,000 years ago was wearing clothes (as opposed to animal hides wrapped around oneself to fend off the cold). Finding this date began with an American researcher’s son coming home from a German school with a note that one of his classmates had lice. Lice can’t survive away from the warmth of the human body for more than 24 hours.

Researcher Mark Stoneking, an evolutionary anthropologist realized that lice could be useful in tracing human migrations. Now in the days when humans were hairy, the lice (singular is Louse) were endemic. Then as humans lost their hair, the lice retreated to the hair on top of the head.

But once humans began to wear clothes regularly, the lice had another place to live, in the fabric of the clothes. These lice needed a way to hold onto the threads and became the body louse. By genetic study of people with lice from different global populations, Stoneking found that body louse (lives in clothes) arouse from mutations from head louse about 72,000 years ago. This is likely when most humans began to wear clothing.

The next big event in our species history occurred about 50,000 years ago in Northeast Africa. There were an estimated 5,000 Homo Sapiens living there. As hunter gatherers, there was a struggle for land and food. Beyond their home area lurked more primitive and brawnier archaic (earlier) species of Homo. But these Homo Sapiens were able to successfully compete and even prevail as small groups moved into Asia and eventually northward into Europe.

The advantage they brought to bear was language. Studies of small groups of disabled people have shown the importance of the FOXP2 gene in speaking. So through mutations in this gene, these African Homo Sapiens were able to communicate with each other, make plans, speak about what to do tomorrow: This gave them a powerful edge on their bigger, brutish adversaries. Within a few thousand years, the speaking Homo Sapiens had reached Australia. Then they traveled northward into Europe, and eventually vanquished the Neanderthals, who had an even larger brain volume, but not the facility of speech.

New program

Our new program for March is “Earth from Distant Stars,” describing how the Earth would appear from distant parts of our galaxy. In viewing any very distant object, there is an effect called “look back time.” If we look at the moon in the evening sky now, we are actually seeing the moon as it was 1.25 seconds ago. This is the time that light takes to travel from the moon’s surface to the Earth.

During the day, we don’t see the sun as it is, but as it was 500 seconds ago, the time it takes sunlight to go from the sun’s surface to the Earth. Similarly, if we look at Sirius, the night’s brightest star, we see it as it was nine years ago, in the year 2000. If we view our Earth from a point on the opposite side of our galaxy (shaped like a pie that’s 100,000 light years across), we would be seeing the Earth as it was about 75,000 years ago, about the time that humans started to wear clothing.

There are some distant star clusters that are 50,000 light years away. The Earth view from these stars would be the Earth of 50,000 years ago, when a few hundred Homo Sapiens (who could speak) left northeast Africa for Asia.

Our free presentations will be on Sundays at 4 p.m. and 7 p.m. today and on March 18, 22 and 29. The Planetarium is in Tawes 302, close by the Lane Center, the Compton Science Center and the Performing Arts Center. Call FSU Planetarium at (301) 687-7799) to request a free bookmark sent to your mailing address.

Bob Doyle invites any reader’s comments or questions: His email is rdoyle@frostburg.edu .