Smithsonian.com

A piece of the elbow from Australopithecus anamensis found in northern Kenya. Image courtesy of Wikicommons

Kenya is a hotspot of human evolution. Birthplace of famed fossil hunter Louis Leakey, the country is home to the remains of at least seven hominid species. Here’s a look at Kenya’s top fossil finds:

1. Orrorin tugenensis: In 2001, a team of researchers reported they had unearthed more than a dozen hominid fossils in the Tugen Hills of western Kenya. The bones date to 5.8 million to 6.2 million years ago, making them some of the oldest hominid fossils. The team, led by Brigitte Senut of the National Museum of Natural History in Paris and Martin Pickford of the Collège de France, determined that they had found a hominid based largely on the species’ thigh, which had telltale features related to walking upright. They named the new species Orrorin tugenensis, meaning “original man in the Tugen region” in the local language. In 2008, an analysis confirmed that the species was indeed capable of walking bipedally. That means Orrorin is in the running for the title of our earliest hominid ancestor.

2. Australopithecus anamensis: A probable direct ancestor of Australopithecus afarensis, A. anamensis lived in East Africa 3.9 million to 4.2 million years ago. The first fossil of this species was uncovered at the site of Kanapoi in northern Kenya in 1965, but the excavators didn’t know what to make of it. Almost 30 years later, in 1994, paleoanthropologist Meave Leakey’s team found similarly aged fossils in the nearby site of Allia Bay. Leakey concluded that the Kanapoi and Allia Bay fossils belonged to a previously unrecognized species that lived a few hundred thousand years before Lucy.

3. Kenyanthropus platyops: Meave Leakey’s team found another new hominid species in 1999. Justus Erus, one of Leakey’s field assistants, found a skull broken in two halves in the West Turkana region. The 3.5-million-year-old skull had many primitive features, including a small brain. But it had several surprisingly modern-looking traits, such as a flat face and small cheek teeth normally associated with the genus Homo. Since then, no other K. platyops specimens have been identified. This has led some researchers to conclude the species isn’t its own species at all. Instead, it may be just a damaged, distorted A. afarensis skull.

4. The Black Skull: In 1985, paleoanthropologists Alan Walker and Richard Leakey discovered a 2.5-million-year-old hominid skull in the Lake Turkana region. Known as the Black Skull, the cranium was darkened by manganese minerals in the soil where it was unearthed. The skull, plus several isolated jaws previously found in the area, resembled the so-called robust hominids—Paranthropus boisei and Paranthropus robustus. The Black Skull had massive molars, flat cheeks and a large jaw. In addition, it had a thick ridge of bone running lengthwise from the top to the base of the skull, called a sagittal crest, where enormous chewing muscles attached. Many researchers think these fossils belong to a species called Paranthropus aethiopicus, a likely ancestor of the later Paranthropus species. Others disagree (PDF) and argue the species’ true name should be Australopithecus aethiopcus. These researchers say the Black Skull is too primitive to be the ancestor of the robust hominids. And their similarities are superficial—an example of parallel evolution, when two closely related species evolve similar characteristics due to similar environmental pressures.

5. The earliest Homo fossil: In 1967, paleoanthropologist Andrew Hill found a bone fragment in the Chemeron Formation of the Tugen Hills. The bone came from the temporal region of a hominid skull, the area near the ear. Comparisons with australopithecines and later species of Homo indicate the bone is probably some early form of Homo. With an age of 2.4 million years, it’s the earliest known Homo specimen.

6. Homo rudolfensis: At the Koobi Fora site in northern Kenya, Bernard Ngeneo found an unusual skull, known as KNM-ER 1470, in 1972. Dating to 1.9 million years ago, the skull’s owner lived at the same time as Homo habilis, the earliest known species of Homo. But the skull’s larger brain size and larger cheek teeth—characteristic of the earlier australopithecines—have led some anthropologists to classify KNM-ER 1470 as a separate species: H. rudolfensis.

7. Turkana Boy: Unearthed in 1984 by prolific fossil hunter Kamoya Kimeu in West Turkana, Turkana Boy is a nearly complete skeleton of an approximately 9-year-old Homo erectus child that lived 1.6 million years ago. The skeleton has helped researchers demonstrate H.erecuts was the first hominid to have a tall body and long legs: Scientists estimate the child was over 5 feet tall when he died and likely would have reached 6 feet had he lived to be an adult.