Overview:

The species that you and all other living human beings on this planet belong to is Homo sapiens. During a time of dramatic climate change 300,000 years ago, Homo sapiens evolved in Africa. Like other early humans that were living at this time, they gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments.

Anatomically, modern humans can generally be characterized by the lighter build of their skeletons compared to earlier humans. Modern humans have very large brains, which vary in size from population to population and between males and females, but the average size is approximately 1300 cubic centimeters. Housing this big  brain involved the reorganization of the skull into what is thought of as "modern" -- a thin-walled, high vaulted skull with a flat and near vertical forehead. Modern human faces also show much less (if any) of the heavy brow ridges and prognathism of other early humans. Our jaws are also less heavily developed, with smaller teeth.

Scientists sometimes use the term “anatomically modern Homo sapiens” to refer to members of our own species who lived during prehistoric times.

History of Discovery:

Unlike every other human species, Homo sapiens does not have a true type specimen. In other words, there is not a particular Homo sapiens individual that researchers recognize as being the specimen that gave Homo sapiens its name. Even though Linnaeus first described our species in 1758, it was not customary at that time to designate type specimens. It is rumored that in 1994 paleontologist Robert Bakker formally declared the skull of Edward Drinker Cope as the “lectotype”, a specimen essentially serving as the type specimen. When Cope, himself a great paleontologist, died in 1897, he willed his remains to science, and they are held by the University of Pennsylvania. But a type specimen must be one examined by the original author who names a species, so Cope’s remains do not qualify.

How They Survived:

Prehistoric Homo sapiens not only made and used stone tools, they also specialized them and made a variety of smaller, more complex, refined and specialized tools including composite stone tools, fishhooks and harpoons, bows and arrows, spear throwers and sewing needles.

For millions of years all humans, early and modern alike, had to find their own food. They spent a large part of each day gathering plants and hunting or scavenging animals. By 164,000 years ago modern humans were collecting and cooking shellfish and by 90,000 years ago modern humans had begun making special fishing tools. Then, within just the past 12,000 years, our species, Homo sapiens, made the transition to producing food and changing our surroundings. Humans found they could control the growth and breeding of certain plants and animals. This discovery led to farming and herding animals, activities that transformed Earth’s natural landscapes—first locally, then globally. As humans invested more time in producing food, they settled down. Villages became towns, and towns became cities. With more food available, the human population began to increase dramatically. Our species had been so successful that it has inadvertently created a turning point in the history of life on Earth.

Modern humans evolved a unique combination of physical and behavioral characteristics, many of which other early human species also possessed, though not to the same degree. The complex brains of modern humans enabled them to interact with each other and with their surroundings in new and different ways. As the environment became more unpredictable, bigger brains helped our ancestors survive. They made specialized tools, and use tools to make other tools, as described above; they ate a variety of animal and plant foods; they had control over fire; they lived in shelters; they built broad social networks, sometimes including people they have never even met; they exchanged resources over wide areas; and they created art, music, personal adornment, rituals, and a complex symbolic world. Modern humans have spread to every continent and vastly expanded their numbers. They have altered the world in ways that benefit them greatly. But this transformation has unintended consequences for other species as well as for ourselves, creating new survival challenges.

Evolutionary Tree Information:

Fossils and DNA confirm humans are one of more than 200 species belonging to the order of Primates. Within that larger group, humans are nested within the great ape family. Although we did not evolve from any of the apes living today, we share characteristics with chimpanzees, gorillas, and orangutans (the great apes), as well as other apes. We most likely evolved from Homo heidelbergensis, the common ancestor we share with Neanderthals, who are our closest extinct relatives.

Questions:

We don’t know everything about our own species—but we keep learning more! Through studies of fossils, genetics, behavior, and biology of modern humans, we continue to learn more about who we are.

Below are some of the still unanswered questions about Homo sapiens that may be answered with future discoveries:

1. Who was our direct evolutionary ancestor? Was it Homo heidelbergensis, like many paleoanthropologists think, or another species?
2. How much interbreeding occured between our species and Homo neanderthalensis?
3. What does the future hold for our species in an evolutionary sense? 

References:

Recommended readings:

McBrearty, S., Brooks, A., 2000. The revolution that wasn't: a new interpretation of the origin of modern humans. Journal of Human Evolution 39, 453-563.

Henshilwood, C.S., Marean, C.W., 2003. The origin of modern human behavior: critique of the models and their test implications. Current Anthropology 44, 627-651.