Evolution of Human

Scientists traced the course of evolution from the origin of life through the extinction of the dinosaurs.  The scientists seen that evolution took many surprising twists and turns to that point.  The subsequent evolution of mammals and humans was just as interesting.  We are primates, as are all the great apes, monkeys, and prosimians (such as lemurs).  The ancestor of all of today's primates lived in the trees, and many of the traits that make us so successful evolved as adaptations to tree life.  For example, the limber arms that allow us to throw balls and work with tools evolved so that our ancestors could swing through trees, and our dexterous hands evolved to hang from branches and manipulate food.  The eyes of primates are close together on the front of the face, providing overlapping fields of view that enhance depth perception--an obvious advantage when swinging from branch to branch.  For the same reason, primates developed excellent eye-hand coordination.

Parental care is essential for young animals in trees, and primates evolved close parent-child bonds.  These bonds, in turn, made it possible for primates to be born in much more helpless state than the babies of most other types of animals.  Although many primate species, including us, eventually moved down from the trees, most primates continue to nurture their young for a long time.  This trait reaches its extreme in humans.  Human babies are nearly helpless at birth and require parental care for more years than the offspring of any other species.  Contrary to a common myth, humans did not evolve from gorillas or other modern apes.  Rather, modern apes and humans share a common ancestor that is now extinct.  Our closest living relatives, chimpanzees and gorillas, shared a common ancestor with us just a few million years ago.

The facet that modern gorillas, chimps, and humans all evolved from the same ancestor has at least two important implications for understanding our existence today.  First, it shows that relatively small genetic differences can make a big difference in species success.  About 98% of the DNA sequences that make up the human genome are identical to the sequences that make up the chimpanzee genome.  Thus, a 2% difference in genetic material is all that separates our current success on the planet from the current predicament of chimpanzees, which survive naturally in only a few isolated locations in Africa.  Second, it suggest that the evolution of intelligence is a complex process.  Gorillas and chimpanzees have been evolving from our common ancestor just as long as we have, but we are the only species building cities and radio telescopes.  This fact raises the question of whether advanced intelligence is and inevitable outcome of evolution. 

Even after hominids (human ancestors) diverged from the ancestors of chimpanzees and gorillas, human evolution followed a remarkably complex path.  Indeed, one of the most pervasive but incorrect myths about human evolution is that it followed a simple pathway from stooped apes to upright humans.  The reality is that there have been numerous hominid species, sometimes with two or more sharing the Earth at the same time.  The earliest fossil skulls that appear to be identical to those of modern humans are about 100,000 years old.  However, even then our ancestors shared the planet with another hominid species, usually called Neanderthals, that was quite similar and may have had a slightly larger brain on average.  The Neanderthals disappeared about 35,000 years ago, and no one yet knows why.

Deciphering the details of human ancestry is a rich field of research.  First, there is no longer a "missing link" in human evolution.  While a few mysteries may always remain, we now know enough from the fossil record and genome comparisons to see a clear path from the earliest microbes to ourselves.  Second, despite the many species of hominids that have come and gone, all modern humans are members of the same species.  That is, while people often focus on outward differences between races, such as skin color of hair texture, all human genomes are virtually identical.  Moreover, any small racial differences that might once have arisen have since been spread across races by the widespread interbreeding of our ancestors.  Any remaining genetic differences between human races are generally much smaller than the genetic variation among the individuals in each race.  The early twentieth century saw the rise of many groups, most notoriously the Nazis, that tried to claim the genetic superiority of one race over others.  But late-twentieth-and twenty-first-century science has shown these claims to be scientifically invalid.