It is our hope that these labeled in vivo chimpanzee brains will assist future researchers in identifying sulci on hominin endocasts, which is a necessary first step in the quest to learn how and when the external morphology of the human cerebral cortex evolved from apelike precursors. The sulcal patterns in these new images also suggest that changes in two gyri that bridge between the parietal and occipital lobes may have contributed to cortical reorganization in early hominins. Our findings, even in a small sample like the present one, overturn published claims that australopithecine endocasts reproduce derived configurations of certain sulci in their frontal lobes that never appear on chimpanzee brains.

These images and sulcal identifications exceed the quantity and quality of previously published illustrations of chimpanzee brains with comprehensively labeled sulci and, thus, provide a larger number of examples for identifying sulci on hominin endocasts than hitherto available. Sulci on the exposed surfaces of the frontal, parietal, temporal, and occipital lobes are identified on the images based on their locations, positions relative to each other, and homologies known from comparative studies of cytoarchitecture in primates. Here, we provide images of lateral and dorsal surfaces of 16 hemispheres from 4 male and 4 female adult chimpanzee brains that were obtained using in vivo magnetic resonance imaging.

The shortage of adequate descriptions of chimpanzee sulcal patterns partly explains why the identities of certain sulci on australopithecine endocasts (e.g., the inferior frontal and middle frontal sulci) have been controversial. However, the few comprehensive descriptions of cortical sulci published for chimpanzees usually relied on post mortem brains, (now) antiquated terminology for some sulci, and photographs or line drawings from limited perspectives (typically right or left lateral views). Paleoneurologists rely heavily on published descriptions of sulci on brains of great apes, especially chimpanzees (humans’ phylogenetically closest living relatives), to guide their identifications of sulci on ape-sized hominin endocasts. Surface traces of sulci that separate the brain’s convolutions (gyri) are reproduced sporadically on early hominin endocasts. We might not be able to fight off a chimp, but we can make some pretty amazing needlepoints.The only direct source of information about hominin brain evolution comes from the fossil record of endocranial casts (endocasts) that reproduce details of the external morphology of the brain imprinted on the walls of the braincase during life. Humans have a lot more fine motor control than chimps: we can do things like play a guitar, paint teeny tiny lines or thread a needle.Ĭhimps can’t, because of the way their neurons activate their muscles-they can’t pick and choose just a few muscle fibers at a time. They say that a big reason chimps can lift heavier things than we can, is that they have less control over how much muscle they use each time they lift. They say chimps are three to five times stronger than humans-something Hawkes would argue isn’t proven-but their explanation for why might still pass muster. But why? Scientific American tries to explain: So apes are definitely stronger than humans, probably around twice as strong. Once he’d corrected the measurement for their smaller body sizes, chimpanzees did turn out to be stronger than humans-but not by a factor of five or anything close to it. An adult male chimp, he found, pulled about the same weight as an adult man. In 1943, Glen Finch of the Yale primate laboratory rigged an apparatus to test the arm strength of eight captive chimpanzees. … But the “five times” figure was refuted 20 years after Bauman’s experiments. The suspicious claim seems to have originated in a flapper-era study conducted by a biologist named John Bauman. Some say that chimps are five to eight times stronger than humans, but those figures come from an old, poorly designed study, says John Hawkes, an evolutionary biologist: Other, more impressive figures often pop up when chimp attacks happen. A 2006 study found that bonobos can jump one-third higher than top-level human athletes, and bonobo legs generate as much force as humans nearly two times heavier. The apes beat us in leg strength, too, despite our reliance on our legs for locomotion. Slate writes:Ī chimpanzee had, pound for pound, as much as twice the strength of a human when it came to pulling weights. In fact, the unfortunate student probably would have been better off had he been attacked by two humans. This summer, two chimpanzees attacked a graduate student at the Jane Goodall Institute Chimpanzee Eden.

Adult chimpanzee vs human skulls