Featured image: The camp of Louis and Mary Leakey at Oldupai Gorge, Tanzania, 1965.

(Continued from The Dawn of Man in Africa–Footprints at Laetoli, https://storiesofeastafrica.com/2024/07/15/the-dawn-of-man-in-africa-footprints-at-laetoli/)

To the casual eye, Oldupai Gorge, in Tanzania’s Ngorongoro Conservation Area, seems much like any other network of scrub-littered ravines draining (whenever it rains) dry rangeland areas in the world. However, it stands out from the rest in being a special place, a UNESCO World Heritage Site yielding up artifacts invaluable to understanding early human evolution.

Oldupai Gorge’s fame reflects its unique geological history:

• Basalt flows from Ngorongoro’s Crater Highlands which flooded the area almost two million years ago.
• The subsequent, intermittent formation of shallow alkaline lakes attractive to a rich diversity of animals, apes and early humans (Lakebed clays aided in fossilizing their remains).
• Periodic volcanic eruptions in the nearby Crater Highlands which added successive layers of ash that helped preserve animal and hominid remains.*
• Geologically recent earth movements which tilted the Oldupai area, creating the stream that cut the ( up to 90 meter / 295 ft deep) Oldupai Gorge, exposing an orderly sequence of nearly two million years of layered deposits containing animal, pre-human, and human artifacts.

* Hominid–Family of erect, bipedal primates including humans together with extinct ancestral and related forms and the gorillas, chimp, bonobo and orangutan.

In this way, Nature first created, and then exposed, a treasure trove of artifacts illustrating human evolutionary history.

All that was needed now was for someone to piece that history together.

Enter Louis and Mary Leakey. Born in Kenya to missionary parents, Cambridge-educated Louis was raised among the Kikuyu, whose language he spoke and about whom he later wrote a book. For her part, Mary, despite receiving only a sporadic education, already was a woman pioneer in the fields of archaeology and paleoanthropology. Their complimentary skills, hers in excavating artifacts and his in interpreting and publicizing them, made them an effective husband-wife team.

Beginning in 1931, the Leakeys spent most of their professional careers excavating Oldupai Gorge’s layered deposits, from the lowest and oldest (1,750,000 years) to the highest and youngest (present day).

Their first major find, in 1959, was a large, robust ape, which Louis Leakey classified as Zinjanthropus boisei (Later classified as Australopithecus boisei, and then reclassified as Paranthropus boisei). He initially considered it to be a direct ancestor of humans because it walked upright and was found with an abundance of faunal remains and rudimentary stone tools (so named because the stones chosen already resembled the final product and were simply altered by chipping off a few flakes). Its massive teeth (for which it was nicknamed Nutcracker Man) implied a diet of coarse plant material.

It was a welcome discovery for the Leakeys who up to this point had, whenever Louis could find enough funds to support their work, spent 28 years at Oldupai uncovering animal fossils and crude stone tools. Zinjanthropus, however, caught the world’s attention, enabling Louis to secure proper long-term financial support–from the National Geographic Society.

But then in 1960, remains of another hominid species, discovered by Mary and her son, John, came to light. Similar in age to Zinjanthropus boisei but smaller in stature, it had smaller teeth and a larger brain, which at 600 cc was 100 cc larger than Zinjanthropus’s. This changed Louis’s mind–Here was the real direct ancestor of man, one more likely to have used stone tools. Louis named the new find, Homo habilis. Handy man.

Still largely ape-like, H. habilis remained partially arboreal (long arms) but ate more meat (implied by its smaller teeth) than apes, and probably scavenged and hunted smaller animals, while still eating lots of plants.

(Note: Present-day thinking is that Paranthropus boisei may, in fact, have been able to make rudimentary stone tools, which it used for butchering carcasses.)

Louis’s and Mary’s announcement that they had found a new species of early human provoked controversy as many experts thought they had too little evidence to support such an important conclusion. Only in the 1980’s, following Richard Leakey’s discovery, in 1972, of Homo habilis remains on the shores of Kenya’s Lake Turkana, did the scientific community fully accept that Homo habilis was a true human ancestor.

The Leakey’s later excavation of Homo erectus (Upright Man) remains in higher level, 0.7 – 1.2 million-year-old, deposits in the gorge, created less of a stir because remains of H. erectus already had been discovered elsewhere (Java in 1892 and China in 1927). Nonetheless, finding H. erectus , Paranthropus boisei, and H. habilis, as well as 17,000-year-old artifacts of H. sapiens (Modern Man) at Oldupai made it possible to demonstrate the full sequence of human evolution at a single site.

At 950 cc, H. erectus had a larger brain than H. habilis. Upright Man also used more sophisticated stone tools, including hand axes and cleavers, had a more modern gait and body proportions (flat face, prominent nose) and sparse body hair, carried out coordinated hunting of medium-large animals (bovines-elephants) and possibly was the first human ancestor to use fire, have a proto-language, and practice monogamy (as inferred from males and females being similar in size). H. erectus also was the first human ancestor to spread from Africa into Eurasia.

Stone Age Homo sapiens, represented by the 17,000 year-old remains excavated at Oldupai Gorge, used stone tools tools characterized by microliths, which are smaller, finer, and sharper than stone tools made by H. erectus. They include spear points and arrow heads. Microliths were advanced technology in their day because they were portable as well as easier to make than the hafts of spears and bows. Thus, when a spear point broke it could be easily replaced without having to make a new haft.

SUMMARY

From the early 1930’s until Mary died in 1996 (Louis died in 1972), the Leakeys were responsible for most of the stone tool and hominid fossil discoveries at Oldupai Gorge (and Laetoli). These discoveries, which were major contributions to understanding human evolution, proved that:

• Humans were far older than previously believed
• Human evolution centered in Africa rather than Asia, as earlier discoveries had suggested
• The earliest humans coexisted with a species of ape which, like them, walked upright.

They also demonstrated the relationship between the evolving features (especially brain size) of increasingly modern species of humans and the sophistication and frequency of use of stone tools.

Louis and Mary Leakey worked at Oldupai Gorge for 41 and 65 years respectively. It was time well spent.

REFERENCES

Bygott, D. 1992. Ngorongoro Conservation Area Guidebook. Tanzania Printers Ltd.

Leakeyfoundation.org.

Ward, C.V. & A.S. Hammond. 2016. Australopithecus and kin. Nature Education Knowledge 7(3)1.

Wikipedia: (a) Richard Leakey, (b) Microliths, (c) Paranthropus, (d) Aistralopithecine, (e) Oldupai Gorge, (f) Homo habilis, (g) Homo erectus.