Last Ape Standing: The Seven-Million-Year Story of How and Why We Survived by Chip Walter

defiantly out of the great lake itself, a disdainful sentinel that stood unfazed by the storms that howled when the seasons changed or the dust devils that spun along its flanks in the hot summer months.
    If you check a map of Africa today, you will notice the slender imprint of this lake we now call Turkana (formerly known as Lake Rudolf). It is still vast, a long, liquid gem that lies on the breast of East Africa, most of it in northern Kenya with just its upper nose nudging the highlands of southern Ethiopia. Today Lake Turkana fails to be as hospitable as it was earlier in its life. The rivers that once drained it are gone, so evaporation is the only exit for Turkana’s waters. That has turned it a splendid jade color and made it the world’s largest alkaline lake. These days the land that surrounds it is mostly dry, harsh, and remote. However, 1.8 million years ago it was an exceedingly fine place to set up housekeeping.
    Life of every kind thrived along Turkana’s shores in the early days of the Pleistocene epoch, despite the occasional ferocity of the weather and the ominous belching of its volcanoes. 8 Crocodiles bathed in its warm waters;
Deinotherium
, an ancient version of the elephant, and both black and white rhinoceroses grazed among the grasslands.Hyenas yelped and hooted, scavenging what they could and hunting flamingos that fed in the shallows, while the grandcousins of lions, tigers, and panthers harvested dinner from herds of an early, three–toed horse called
Hipparion
. The lake, the streams and the rivers that fed it, and the variability of the weather made the area a kind of smorgasbord of biomes—grasslands, desert, verdant shorelines, clusters of forest and thick scrub. The bones of the extinct beasts that lie by the millions in the layers of volcanic ash beyond the shores of Lake Turkana today attest to its ancient popularity.
    The existence of a habitat this lush and hospitable wasn’t lost on our ancestors any more than it was on the elephants, tigers, and antelope that roamed its valleys. In fact it was so well liked that
Homo ergaster
(left),
Homo habilis
, and
Homo rudolfensis
were all ranging among its eastern and northern shores 1.8 million years ago, sharing the benefits of the basin with their robust cousin
Paranthropus boisei
. As many as a million years earlier,
Paranthropus aethiopicus
came and went along the northwestern fringe of the lake, and half a million years before that the flat–faced one,
Kenyanthropus platyops
, braved Turkana’s winds and watched its volcanoes rumble and spew.

    Homo ergaster
    Despite decades of sweltering work, paleoanthropologists have yet to categorically determine which of these humans who trod the shores of Turkana led directly to us, but it is possible to make an informed guess, at least based on the limited evidence scientists have to work with. We already know
Homo habilis
is out of the question, an evolutionary dead end unrelated to
Homo erectus. Homo rudolfensis
is also unlikely because he bears such a strong resemblance to
Paranthropus boisei
and his robust ancestors. He may have been a bridge species of some sort.
Boisei
himself would seem not to qualify given that he wasn’t gracile (we are) and possessed the smallest brain of the group, the largest jaws, and the most apelike features.
    That leaves
Homo ergaster
, “the worker” (
ergaster
derives from the Greek word, meaning “workman”), formerly consideredan example of
Homo erectus
. Truthfully,
ergaster
wouldn’t seem to be a promising candidate for a direct ancestor either, except for one remarkable fossil find that has been, after some heated debate, assigned to the
ergaster
line. In the scientific literature he is known as Turkana (or sometimes Nariokotome) Boy because Kamoya Kimeu, a paleoanthropologist who was working at the time with Richard Leakey, came across him on the western shore of Lake Turkana.
    His discovery first stunned his fellow anthropologists and then the