Oct 05 2010

Archeogenetics I: Bottlenecks and Superhighways

Published by at 6:01 am
Under Archeogenetics | Paleobiology

A

fugue is a musical composition in which one or two themes are repeated or imitated by successively entering voices and developed in a continuous interweaving of the voice parts. It is a much used device in classical music, where often one section of the orchestra will start a melodic line, to which other sections enter in contrapuntal fashion, each starting at the beginning and producing an often hypnotic and undulating melody.

Our African legacy is a similarly fugue-like story, as at different times and in different groupings, humans struck out of Africa, one at a time, with fractions of the group returning and new groups setting out again and again.

We belong to a species group called Homo sapiens sapiens (“modern wise man”). We are possibly descendants of Homo erectus (“upright man”), who lived in Africa at least about two million years ago, although like everything in anthropology, there are arguments pro and con.

Homo erectus would bear a striking resemblance to modern humans, but he had a smaller brain, about 75% of our modern day version. Despite his more modern looks, evidence suggests that he could not produce the complex sounds of our present day speech. H. erectus was probably the first true hunter-gatherer, or maybe more accurately hunter-scavenger. Migrating into Asia, probably following the herds of great mammals such as the mammoths, he left evidence of his existence as far as China (“Peking Man”). He was a great tourist; evidence suggests that he spent time on the French Riviera and remains dating over one million years old have been found in India, Pakistan, China and Indonesia. His presence in Asia initially baffled early anthropologists, and led more than a few to conclude that Asia, not Africa, was the birthplace of modern man.

Ashes to ashes..

However, for reasons not really known, once out of Africa Homo erectus seemed to have stagnated and died out. However, some anthropologists believe that the Homo erectus that stayed in Africa continued to evolve and eventually became Homo sapiens; however other experts do not concur. This had led to two opposing theories. The Multiregional Hypothesis holds that evolution has occurred through a single widespread human species -Homo sapiens- changing and evolving as it spread throughout the world. This idea directly challenges the Out of Africa Model, which claims Homo sapiens evolved recently as a new species in Africa, and then dispersed throughout the Old World, replacing the existing human populations without mixing with them. The genetic evidence seems to support the Out of Africa Model better than the Multiregional Hypothesis, though the jury still out.

The word Paleolithic is Greek for “Old Stone Age” and it extended from the point from where we began to use simple stone tools to roughly the point where we began to harness the power of food domestication and agriculture, at which time begins the Neolithic or “New Stone Age.”

We’ll pick up the story again about 90,000 years ago, when the grandfather of all modern people was born in Africa. As we will see later on, this does not mean that he was the only man alive at the time; it just means that he is as far back as we can go to find a most common ancestor. Certainly, there were thousands of other humans around; however, over the ages their genetic lines just died out. As old as that is, he’s a whippersnapper next to our genetic grandmother, who clocks in at a robust 150,000 years ago.

Although the oldest, or Lower Paleolithic Period is thought to extend almost two million years into the past, most modern type human development took place from about 300,000 years ago to about 10,000 years ago, during the Middle and Upper Paleolithic Periods, a time that may have witnessed the beginnings of a full-featured use of language and branching off much of our current day physical and genomic distinctions. At this time, although it is not completely certain, the early proto-languages may have begun.

Fire and language: Quite the combination.

At archeological sites, tools are often more abundant than bones. Humans have only about 200 bones, and many of these contain edible substances, such as marrow or brain, so you don’t see very many of them, but stones you do see; especially tools made of very hard materials, such as quartz and obsidian. The techniques of making these tools were handed down from generation to generation and the sequences of these techniques became a trademark of that group. A similarity of tool-making techniques among groups of people tells us that knowledge as well as genes was exchanged.

Fire is a discovery rather than an invention, and prehistoric humans certainly knew about it. They may have even witnessed lightning striking an old tree, causing it to burst into flames –or even the sun, shining on dry leaves, causing them to smolder and ignite.

Fire could be considered a tool, since it frightens off predators, keeps people warm and dry, helps cook food, and provides a center for the home territory of a group of people. Here our early ancestors could sit at night, warm and secure, talking over the day’s events, seeing each others faces reflected in the fire. As one classical anthropologist put it:

Human beings convert energy drawn from outside their own bodies into social structure, and the greater the amount of energy consumed, all things being equal, the more complex the social structure.

Stone tools and fire gave our early ancestor a more complex social structure, and all three combined to provide a control over the environment that his ancestors could never have dreamt about. But it gave him something even greater than simple control of his immediate world. It gave him the confidence to explore the far reaches of his curiosity. And that meant travel.


Excerpted from:

  1. D’Adamo PJ. ‘Archeogenetics’ in: Fundamentals of Generative Medicine, Volume I (2010) Drum Hill Books, Wilton CT USA

One response so far

One Response to “Archeogenetics I: Bottlenecks and Superhighways”

  1. Joli says:

    Travel and tasting new flavors along the way.. and still doing it today!

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