![]() Range elevation 0 to 2,750 m 0.00 to ftĪdult chimpanzees have a head and body length ranging between 635 and 925 mm.Some populations are known to inhabit primarily savanna habitat. Although they are typically thought of as living in tropical rainforests, they are also found in forest-savanna mosaic environments, as well as in montain forests at elevations up to 2,750 m. ( Nowak, 1999)Ĭhimpanzees utilize a great diversity of habitat types. In the far eastern portion of the range, from the northwestern corner of Zaire into western Uganda and Tanzania, P. troglodytes troglodytes inhabits forested regions. From the Niger river to Congo, in the central portion of the range, P. Pan troglodytes verus occurs in the western portions of the range, from Gambia to the Niger river. There are three recognized subspecies of common chimpanzee. They are found from Gambia in the west to Uganda in the east, excluding the region bordered by the Congo and Lualaba rivers in central Zaire (Congo) where their sister species, bonobos ( Pan paniscus), are found. They are distributed from about 10 degrees N to 8 degrees S, and from 15 degrees W to 32 degrees E. But over time, human and chimpanzee brains evolved in several different and important ways.Chimpanzees ( Pan troglodytes) inhabit the tropical forests of central Africa. The brains of the earliest humans were similar in size to those of chimpanzees. Humans are primates, and chimpanzees are our closest living relatives. To obtain an accurate measure of brain size, scientists remove an endocast from the braincase and record its volume, or use CT scanning to measure the inside of the braincase. Scientists also make artificial endocasts to study, like the ones above. Sometimes sediments fill the cavity and harden, making a natural endocast. They deteriorate, leaving a cavity inside the braincase. How are endocasts made?īrains do not fossilize. They represent the size and shape of the brains that once occupied the braincases. Evidence of ancient brainsĮndocasts are replicas of the insides of early and modern human braincases. To construct this graph, scientists measured the brain cavities of more than 160 early human skulls. A large brain capable of processing new information was a big advantage during times of dramatic climate change. The bottom graph shows how brain size increased over the past 3 million years-especially between 800,000 and 200,000 years ago. To construct this graph, scientists studied fossils of tiny organisms found in ocean sediment cores. Notice how much the fluctuations increased between 800,000 and 200,000 years ago. The top graph shows how Earth’s climate has fluctuated over the past 3 million years. Graphs showing changes in climate and changes in braincase volume. As the environment became more unpredictable, bigger brains helped our ancestors survive. Larger, more complex brains enabled early humans of this time period to interact with each other and with their surroundings in new and different ways. Human brain size evolved most rapidly during a time of dramatic climate change. These challenges, along with an increase in body size, led to an increase in brain size. Brain and body size increaseĭuring this time period early humans spread around the globe, encountering many new environments on different continents. Brain size increases slowlyĭuring this time period, early humans began to walk upright and make simple tools. The modern human brain is the largest and most complex of any living primate. Over the course of human evolution, brain size tripled. That was a big advantage to early humans in their social interactions and encounters with unfamiliar habitats. Large, complex brains can process and store a lot of information. Hurlbert, Smithsonian Institution)Īs early humans faced new environmental challenges and evolved bigger bodies, they evolved larger and more complex brains. Science, Religion, Evolution and Creationism: PrimerĮndocasts of Homo erectus (left) and Homo sapiens (right) illustrate rapid increase in brain size.Members Thoughts on Science, Religion & Human Origins (video).Teaching Evolution through Human Examples.Digital Archive of Ungulate and Carnivore Dentition. ![]() Adventures in the Rift Valley: Interactive.Smithsonian National Museum of Natural History The Smithsonian Institution's Human Origins Program Main Menu
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