HUMANPAST.NET

Environment                  2 Million BC
Africa
Southwest Asia
Egypt
Indus Valley
China
Europe
South America
Mesoamerica
North America
Other

In General

It is an inescapable fact of genetics that all people alive in the world are genetically related, and that at some point an individual existed whom we all claim as an ancestor. The only points of debate are how long ago that ancesor lived, and where. DNA data suggests all modern humans are genetic descendants of one small inbred group of prehistoric Africans.(18)

The "Total Replacement," "African Origins," or "Eve" model contends that modern humans evolved first and only in Africa and only a few hundred thousand years ago or less, and then migrated to the rest of the world, displacing all other hominid forms, and with little or no genetic interchange between them. If this is true, then, as interesting as those many European and Asian fossils and sites of hundreds of thousands of years ago are, the people who left these remains had almost nothing to do with us in terms of our physical or cultural heritage. This is a difficult premise for many anthropolgists to accept, because so much of what we know about human evolution has been based on sites such as Zhoukoudian, in China, Toralba-Ambrona, in Spain, etc.(18)

Alternatively, the "Multiregional Evolution," "Continuity," or "Candelabra" models propose that: sometime between about 1 million and 2 million years ago a generic Homo ancestor or ours spread out across the warmer latitudes of Africa, the Middle East, Asia, and possibly the southernmost fringe of Europe; then, with the passage of the millennia, although these groups began to diverge somewhat as they adapted to local and different environments, across the whole range of Homo they were evolving toward Homo spaiens as a result of gene flow that connected all human groups to some extent and because they were all under similar evolutionary selective forces as genralized hunter-foragers; so they all converged at about 30,000 years ago as one species, Homo sapiens--but with the physical differencess that distinguish modern Europeans from, for example, modern Chinese.(18)

Today the north pole is positive and the south pole is negative, but these were reversed in some periods, such as for most of the period between about 700,000 and 1.6 million years ago.()

Within the Pleistocene alone - approximately the last two million years - there have been eight magnetic reversals, four normal and four reversed. They are named after either their discoverers, as in the Matuyama-Brunhes at 730,000 years ago, or after places, as in the Olduvai event beginning at 1,880,000 years ago and ending at 1,660,000 years ago. Paleomagnetics offers a well-documented way of assessing where one is in time by examining either the natural remnant magnetism of a rock or the orientation of magnetic particles within sediment, and then assessing "normal" or "reversed" polarity. If one has a reliable sequence of reversals, and one knows approximately where one stands in time, then it's feasible to get an "absolute" date for a layer sandwiched between a series of reversals. The longer the sequence, the better the result. (142)

Africa

By about 1.8 million to 1.7 million years ago, at the last glimmer of the Pliocene and the dawn of the Pleistocene, a new version of us appeared in east Africa - not coincidentally, with a better tool kit. Named Homo ergaster and equipped with a substantially larger body (the males may have reached six feet in height) and a proportionately bigger brain than its predecessor's, this species not only was fully adapted to terrestrial life but could also cope with climatic extremes its predecessors could not survive. Homo ergaster appeared in an Africa where the temperature and precipitation regime was changing from coolish and moister to very warm and very dry. They had attained the same body size as essentially modern humans, had lost the hairy body covering of their predecessors, and were probably the first of our remote ancestors to be able to cope with genuinely arid environments. Indeed, with a few minor differences, Homo ergaster is anatomically modern - but only from the neck down. (130)

Drier conditions in Africa led to a more extensive invasion of the savanna into the forest areas, putting more pressure on those species that relied on the woodlands for survival. By two million years ago African mammals, forest-dependent species, were - across east, north, and southern Africa - replaced by grassland-dependent species. (142)

Southwest Asia

 

Egypt

 

Indus Valley

 

China

 

Europe

 About 3.2 Million years ago, when some of our first bipedal ancestors appeared, massive glaciers had spread over northern lands. These glaciers had grown even larger by 2.5 million years ago, and about 1.6 million years ago, when our earliest ancestors were radiating from Africa, climates began fluctuating, with long periods of intense cold folowed by periods that were nearly as warm as climates of today.(5)

South America

 

Mesoamerica

 

North America

About 3.2 Million years ago, when some of our first bipedal ancestors appeared, massive glaciers had spread over northern lands. These glaciers had grown even larger by 2.5 million years ago, and about 1.6 million years ago, when our earliest ancestors were radiating from Africa, climates began fluctuating, with long periods of intense cold folowed by periods that were nearly as warm as climates of today.(5)

Other