Homo habilis

Homo habilis is an ancient species of hominid believed to be closely related to the evolutionary line that produced modern humans. The species, which is distinguished by its larger brain size and smaller facial features, lived between 1.5 and 2.3 million years ago on the grasslands of eastern Africa.

The first fossil remains were uncovered in the early 1960s and were initially linked to the discovery of stone tools from the same era and region. For this reason, the archaeologists named the species Homo habilis, Latin for “handy man.” They believed Homo habilis was a direct descendant of modern humans and the first in our line to use tools. However, later discoveries have cast doubt on both theories, with some scientists now placing the species on an extinct branch of the human family tree.

Background

In scientific classification, humans are a species of primate that belongs to the family Hominidae, also called hominids or great apes. Other types of hominids include gorillas, chimpanzees, and orangutans. Scientists believe that primates first evolved about 55 million years ago, and the first hominids appeared about 15 million years ago. Sometime about 8 million years ago, creatures that would become the ancestors of modern humans and chimpanzees split off from gorillas on the evolutionary tree.

When a period of global cooling about 5 or 6 million years ago caused the African forestland to shrink, some of these creatures began to leave the trees and venture out upon the grass plains. The animals that stayed behind in the trees became chimpanzees and bonobos. Those who left eventually began to stand upright and walk on two feet. The first of these creatures are believed to have evolved about 4.4 million years ago. Known as Australopithecus, or “Southern Ape,” they had brains only slightly larger than a chimpanzee, feet that could grasp objects, and long, chimp-like arms with curved fingers.

One species, called Australopithecus anamensis, lived in Ethiopia about 3.8 million years ago and is believed to be the oldest-known direct human ancestor. Eventually, Australopithecus evolved to become less chimp-like and develop more human characteristics. This evolution led to a new type of creature with an increased brain size, reduced facial features and jawbone, and the ability to use primitive technology such as stone tools. Scientists classified this creature as the genus Homo, a category that encompasses all species of humans. This includes extinct species such as Homo neanderthalensis, as well as modern humans, or Homo sapiens.

Overview

Prior to the 1960s, archaeologists theorized that the path of human evolution led from Australopithecus to a species of early human called Homo erectus, or “upright man,” and eventually to Homo sapiens. Then, in 1960, a team of archaeologists led by Louis Leakey discovered fossilized teeth and a partial skeleton at Olduvai Gorge in Tanzania. The fossils were dated to about 1.5 to 2.3 million years ago and showed evidence of a larger brain and body than Australopithecus. Features of the hands and feet also suggested the creature may have been able to use stone tools. In the 1930s, Leakey had been the first to discover evidence that stone tools were used in the Olduvai Gorge between 1.5 and 2.5 million years ago.

Leakey published his findings in 1964, claiming the discovery was that of a previously unknown species of human he called Homo habilis. Because he had found the fossils in the same area and geological time period as the stone tools, he linked the two together and theorized that Homo habilis may have been the first human ancestor to use tools. The archaeologists also placed Homo habilis as the first member of the genus Homo and a transitional species, linking the chimp-like Australopithecus to the more human Homo erectus.

Leakey’s claims were controversial at the time they were published and have only been called into more question as additional discoveries have been made. In the 1980s, archaeologists uncovered fossils that showed Homo habilis had more pronounced chimp-like arms and legs than previously believed. Then, in 2015, stone tools dating back to 3.3 million years ago were discovered in Kenya, casting further doubt on the idea that Homo habilis was the first tool user. Scientific advancements have also shown that the path from Australopithecus to the line of modern humans was not so straightforward, and early Homo evolution was a complex, branching process rather than a linear progression. As a result, many archaeologists now believe that Homo habilis may have been one of several species of Homo living in Africa at about the same time. Some Homo habilis fossils have now been reclassified as another species called Homo rudolfensis, named after Lake Rudolf in Kenya. Homo rudolfensis fossils have larger brains, larger teeth, and a more ape-like face and may have been an evolutionary descendant of Homo habilis.

The classification and naming of fossils is a complicated and often controversial process, with disagreements common among archaeologists. The idea that Homo habilis is part of the direct lineage of modern humans is still accepted in some scientific circles, although it is no longer widely accepted. Many experts believe the species’ chimp-like characteristics are too much to overlook and think it should be reclassified as Australopithecus habilis and moved into a side branch of the human family tree. Further, scientists have more recently determined the earliest definitive Homo specimen dates to 2.8 million years ago, predating Homo habilis.

From studying modern fossil evidence, researchers found Homo habilis had a body type more similar to an Australopithecus, averaging about 4.3 feet (130 cm) tall for males and 3.6 feet (110 cm) for females. However, their brain was larger than that of Australopithecus, averaging about 37.2 cubic inches (610 cubic cm), or about 1.7 percent of their total body weight. Because of the larger brain, the shape of their skull was rounder and showed the first appearance of a slight, human-like forehead. The teeth of Homo habilis were smaller than Australopithecus and arranged in a more rounded fashion, similar to modern humans.

The species lived on the grasslands of eastern Africa and walked upright on two legs, though their short legs and longer arms were more chimp-like. The shape of their hands and finger bones represented a transition between apes and modern humans. The proportion of the species’ finger bones also suggests that Homo habilis was capable of gripping objects such as tools. While archaeologists are not sure the species was the first to use tools, it seems likely that Homo habilis did use chipped and flaked stones to scrape meat from the bones of dead animals. Evidence suggests that they were mainly vegetarians, but they also began to incorporate some meat in their diet.

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