Dave Taylor's African Safari: The Missing Factor: Human Beings - Introduction

The Missing Factor: Human Beings
Introduction
Page 1

Today, much of the Serengeti-Mara ecosystem is protected from humans. Serengeti National Park was set aside for the animals. Resident tribes were moved out of their traditional areas within the park's borders. The same is true within the core area of Kenya's Masai Mara. Ngorongoro Conservation Area allows the Maasai and other tribes to pursue their traditional lives within its boundaries. There, only the crater itself is reserved primarily for wildlife. The other wildlife units that make up the Serengeti-Mara ecosystem also allow humans to live and work in them.

Much of the research done at the Serengeti Research Institute tries to unlock the secrets of the natural world. We have gained insights into the relationship of predators and prey there without the interference of mankind. However, it must be remembered that mankind has been a part of this ecosystem for as long as our species has been around. This book looks at the various Hominid species that lived in the Serengeti-Mara ecosystem in the last 3 million years.

Cradle of Mankind

Within the Serengeti-Mara ecosystem's boundaries lie the Olduvai Gorge and Laetoli archeological sites. Both are protected within the Ngorongoro Conservation Area. These two spots preserve a record of human history in the area dating back at least 3.6 million years.

Olduvai Gorge is about 50 kilometers long (30 miles) and, in places, 90 meters (90 yards) deep. To the east lie the Crater Highlands including Ngorongoro Crater. It is the seasonal runoff from these nearby mountains that created the gorge, gradually eroding the soft volcanic soils and revealing its hidden treasures.

At one time, the area that we now know as Olduvai was once the shoreline of a shallow lake. Along its shores lived a much richer array of wildlife than even the Serengeti possesses today. There were several species of elephants (including mastodons), giant and dwarf giraffes, buffalo twice the size of today’s, saber-toothed cats, extinct tigers, giant baboons and even wildebeest much like the ones that continue to migrate through the gorge today.

It has always been an area rich in wildlife. Among these species walked some of our earliest relatives.

One Day at Laetoli: Australopithecus afarensis

At Laetoli are preserved the ancient tracks of two hominids, probably walking together, and a third one that passed by later. All three are believed to belong to Australopithecus afarensis. Discovered by Mary Leakey in 1976, the site revealed a snapshot of daily activity on the plains 3.5 to 3.7 million years ago.

(Author’s note: an even older australopithecine was found in northern Kenya. It was named A. anamensis and is dated at 4.1 million years old.)

On that day, the nearby volcano, Sadiman, erupted and showered the area with gray ash coating the plain with a thin layer.

Across this layer walked the three hominids. Guinea fowl also scurried by leaving their trails behind. Tracks show that hares were abundant. Giraffes also walked across the ash field. These species still live in the area today.

Other species, now extinct, left their tracks too. Among them was Deinotherium, an elephant with downward curving tusks, and a three-toed horse, Hipparion.

Soon after these animals left their tracks, a light rain dampened the ground, setting the tracks. A few days later, a second puff of gray ash covered the scene and preserved it.

At Laetoli A. afarensis is known only from the footprints the three left behind. Fossils of the species have been found in other locations and together with the tracks they present us with an image of this creature. Its brain case (400 cc- cubic centimeters) was much smaller than the accepted minimum for it to be classed as Homo (600 cc) so it is not yet human. It is however, not an ape, but an animal more closely related to humans than our closest living relative, the chimpanzee.

A. afarensis was 1.2 to 1.4 meters (4 - 4 feet 7 inches) tall. To our eyes it may have indeed looked like a chimpanzee but there would have been one striking difference; this animal walked like we humans do today. It was bipedal! Until the discovery of the tracks there was much debate about how early in our family tree our ancestors walked on two legs. No one really believed the date would be back as far as 3.5 million years ago.

The significance of the find radically changed the way anthropologists look at our family tree. Here was an upright, bipedal hominid that was clearly further advanced than had been believed possible. What other traits did it share with us? There is no evidence of tool using. With later species, fossil bones were often found associated with stone tools.

The lack of stone tools does not mean that this animal did not use branches as clubs or for digging.

Its diet probably consisted of tubers, fruits, berries, leaves, insects and the occasional rodent or young gazelle.

The big question that anthropologists want answered is where this species fits into our evolution. Did it give rise to both A. boisei and A. africanus (a species found in South Africa) or to just one of these species? Is it a direct ancestor of Homo sapiens? These questions await further discoveries.

Olduvai Gorge

Less than an hour’s drive to the north lies Olduvai Gorge. It does not date back as far as Laetoli but it is a rich treasure chest of fossils. Its uniqueness lies in the circumstances of its creation.

Nearly two million years ago, a volcano poured out a layer of lava on top of which all of the fossil bearing layers were laid down. Since almost all of the 90 meters (295 feet) or so of soil and rocks above this layer are volcanic in origin, they can be accurately dated by the potassium-argon technique. This technique, performed on soil samples in a laboratory, measure the decay of radioactive isotopes that break down at a given rate.

Nearly two million years of volcanic deposits were laid down in sequence. This means that a fossil found at any given spot was older than one found above it and younger than one found below it.

Due to the changing environments over that period of time, a diverse and rich plant and animal community flourished and died here. Many of these left plentiful remains that were fossilized in the sediments of a shallow soda lake. These conditions were ideal for preserving bone.

Recent faulting in the region tilted the Olduvai area, creating new drainage patterns. A seasonal river cut through the area creating the present gorge and revealing the layers of fossil bearing soils.

Geology and Ecology of Olduvai Gorge

About 1,890,000 years ago, the volcano Olmoti erupted and thick lava formed the base of the Gorge. Water could not soak through the lava and a lake soon formed. The lake was only 5 kilometers wide and 10 kilometers long (3 miles by 6 miles). Although much smaller, it was similar in chemical make up to today's Lake Manyara. It was shallow and alkaline. Flamingos fed in it as did pelicans and cormorants. Extinct forms of hippopotami waded in the freshwater streams that drained into it. Crocodiles were common. Fish included tilapia and catfish. Surrounding the lake were wooded shores and papyrus swamps.

The lake expanded and shrunk several times. Nearby volcanoes lay down layers of ash which formed the clays of Bed I and Lower Bed II (see chart left).

Animals living around the time Bed I was created include a large lion-like cat, a saber-toothed cat, hyenas, jackals, at least two species of elephant, white rhinos (now extirpated from Kenya and Tanzania but re-introduced into some parks), a giraffe much like today's species and Sivatherium (a giant short-legged giraffe with large, sweeping horns). Many of the species, such as Sivatherium, found were known from Asia and Europe. Their discovery at Olduvai indicated land bridges connecting the continents.

One animal, now long gone from the Serengeti-Mara, still survives in the Zaire rainforest. The okapi once roamed these ancient plains but today is found only in dense forests. It was not until early in the twentieth century that it was discovered.

More Extinct Fauna

Bed I also produced a species of giant pig which Louis Leakey named in honor of his wife; Afrochoeus nicoli. (Her maiden name was Nicol.) The pig was the size of today's rhinos and its tusks were over 1 meter (1 yard) long. This pig was related to the warthogs that still live in the area. Another species of extinct pig is related to the bush pigs while a third is related to the giant forest hog. Another eight species of extinct pigs have no surviving descendants.

Two species of horses are found in Beds I to IV. One had three toes while the other resembled today's zebra. A distinctly unhorse-like animal, the chalicotheres, were found in Bed I. This animal had a herbivore's teeth, thick legs and long sharp claws that may have been used for digging up tubers. Surprisingly, it is related to horses and tapirs. Insectivores, hares and rodents have been found in all beds too. Antelopes were also common, including a species of wildebeest.

Other extinct fauna include:

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