In the final comparisons of DNA from cell nuclei, the forest and savanna elephants fell into distinct groups.
Savanna and forest elephants interbreed occasionally though Roca's group found little evidence for recent mixing.
Without fire, shrubs thrived, and today many former savannas are a tangle of undergrowth beneath tall trees.
They called it the begetation forest, but I believe they were describing savanna.
Since 1980, South American ranchers have planted roughly 35 million hectares with these varieties because they tap water and nutrients from the poor savanna soils more efficiently than native species.
At one research site, a pasture with deep-rooted grass stored 13 percent more carbon than a neighboring savanna did.
Our adaptation to the savanna habitat (it was then a bit more wooded and lush than the driedout East Africa of today) enables us to spot the animals wishing to prey upon us soon enough to elude them (by climbing one of those trees) or kill them in self-defense.
Every species has a "right" habitat, and the savanna is ours, the open woods, not the deep forest.
A relatively sudden drop in atmospheric carbon dioxide - which favored plants that use carbon dioxide efficiently during energy production sparked the spread of savannas, argued Thure E.
But the grasses and plants that make up savannas had already existed for millions of years in much more variable environments.
To top it off, Falk's scenario of robust australopithecines who put down roots in moist, wooded areas, while their gracile counterparts roamed the savannas and developed bigger brains, presents an unsupported, "cartoon-like" picture of hominid evolution, Kimbel contends.
africanus and later human ancestors worked up a sweat under the hot savanna sun by hunting and scavenging for meat and by trekking long distances in search of edible leaves and fruit, Falk says.
Previous excavations have indicated this ancient savanna
supported more abundant and diverse species of antelope than known earlier in Africa.
Other attempts to use the ecology of modern African savannas as a window to the past are under way.
This drawback is outweighed by the need for data on carcass use and seasonal variation of carcasses in modern savannas, says Lewis Binford of the University of New Mexico in Albuquerque.