What is the Evolutionary History of Humans?

Michael Anissimov
Michael Anissimov

The evolutionary history of humanity begins at least 6-7 million years ago with the fossil ape Sahelanthropus tchadensis, which displays both human and ape-like features. Sahelanthropus may be the common ancestor of chimpanzees, gorillas, and/or humans, an early ancestor of humans, an early ancestor of chimps, an early ancestor of humans, or a completely different lineage to all of the above. In any case, it pushed back the likely date of chimp/human divergence by several million years, which based on early molecular studies was though to be 3-5 million years ago. Such a late divergence is no longer accepted among the anthropological community.

A nuraghe, a Bronze Age structure in Italy.
A nuraghe, a Bronze Age structure in Italy.

Shortly after 6-7 million years ago, or whenever the evolutionary history of human ancestors split from chimps, the fossil record continues with Orrorin tugenensis (6.1-5.8 mya), the earliest human ancestor with evidence of bipedal locomotion; Ardipithecus (5.5-4.4 mya), another upright-walking species that nonetheless had a brain and body similar to that of a chimpanzee; the famous Australopithecus (4-2 mya), a "gracile australopithecine" represented by the fossil "Lucy;" Kenyanthropus (3-2.7 mya), one of the first known apes in evolutionary history with a flat face; and Paranthropus (3-1.2 mya), a "robust australopithecine," with a sturdy build and brain size approaching 40% of modern humans.

Neanderthals were members of the genus Homo that inhabited Europe prior to the appearance of modem Homo Sapiens in the region.
Neanderthals were members of the genus Homo that inhabited Europe prior to the appearance of modem Homo Sapiens in the region.

Around 2.2 million years ago, the genus Homo appeared in evolutionary history, coexisting with Paranthropus and other human-like apes that lived at the time. This genus was a huge intellectual improvement on what came before it, and one of its earliest members, Homo habilis, has a name that means "handy man." That's because this was one of the first animal species to master stone tool technology, though there is evidence that Australopithecus garhi, dated to 2.6 million years ago, was probably a skilled stone tool-user as well. This marked the beginning of the Stone Age, which continued for millions of years until the Bronze Age began just 5,300 years ago.

Cro-Magnons, an early Homo sapiens population, are credited with creating the cave paintings at Lascaux, France.
Cro-Magnons, an early Homo sapiens population, are credited with creating the cave paintings at Lascaux, France.

The most important species in the evolutionary history of humans are our immediate relatives: the members of genus Homo. The word "Homo" simply means "man" in Latin, and these beings were indeed close to man, with large brains, an upright posture, social natures, and tool-using capability. Unfortunately, they are all now extinct, so we'll never know what they were really capable of, or how they communicated with one another. These important human relatives include Homo habilis, Homo rudolfensis, Homo ergaster, Homo georgicus, Homo antecessor, Homo cepranensis, Homo erectus, Homo heidelbergensis, Homo rhodesiensis, Homo neanderthalis, Homo sapiens idaltu, and Homo floresienses. Genetic material left behind by some of these species is being studied and will shed important insight on their relationship to present-day humanity.

Composite tools and weapons, including spears with sharpened stone or bone tips, began to appear after the Middle Paleolithic began 300,000 years ago.
Composite tools and weapons, including spears with sharpened stone or bone tips, began to appear after the Middle Paleolithic began 300,000 years ago.
It is believed that Homo erectus, which may have been the first member of the genus Homo to leave Africa, diversified into several regional populations.
It is believed that Homo erectus, which may have been the first member of the genus Homo to leave Africa, diversified into several regional populations.
The human split from chimps forms part of evolutionary history.
The human split from chimps forms part of evolutionary history.
Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Discussion Comments

pastanaga

@umbra21 - There must have been pressure on us at some point to grow more intelligent though, or we would never have ended up where we are today. I've heard people speculate that human success as a species has got more to do with our ability to empathize and socialize than it does with intelligence per sec, but if that was the only thing to it, I don't think we would have developed thumbs to go along with our tool making abilities.

umbra21

@bythewell - Often people who lived before the modern age were much shorter than we tend to be, but that has got a lot more to do with nutrition than it does with evolution.

I do think that evolution can work that quickly and there are definitely examples of it working within a few generations if the selection pressure is strong enough. But I don't think there has been that much selection pressure on people to grow more intelligent, especially in the last few thousand years. Intelligent people might enjoy more comforts while they are alive (although even that is debatable) but they don't necessarily have more children. Until recently they probably didn't even have that many more surviving children, since no one understood what caused sickness or how to stop it.

bythewell

I remember having an argument with my father a while ago about whether or not an Ancient Egyptian, who was magically transported to the modern world as a baby and raised as an average American, would be as smart as the average American. Dad seemed to think that we had evolved genetically since then to be smarter and I thought that we hadn't evolved that much in the last few thousand years. I mean, if you look at some of the things the Egyptians did, you would think they were smarter than us and as far as I know the remains that have been found don't have any radical differences.

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