Our line had split off from the chimpanzees but a lot of work still needed to be done. A lot of arrogant humans refuse to accept chimps as their heritage. Just out of curiosity, what percent of the chimpanzee (our last common ancestor) DNA is the same as ours, the home sapiens DNA?
10%? 50%? Not 75%, for goodness sake. No! Must be less than that.
At this point, science can quite accurately compare human DNA to that of other animals. For chimpanzees, the correct answer is 98%. As your fetus grew inside your mother, the development included all of those steps, beginning to end. You are a current event made out of history.
That point being made here is that the story of “How Did We Get Here?” is not just a curiosity; it is YOU. Your DNA has strands common to every other living thing, even the lowly bacteria, which shares 8% with you. The capability to show all those emotions seen as you got here were passed onto homo sapiens.
Traits changed slowly over time – traits like walking upright, hand dexterity, which included an “opposing thumb” used to thread a needle or write a letter. Tools developed, at first simple tools like using a sharp rock for cutting, to much more complex tools, like spears and sharp points. Cooking meat began, allowing for changes in the stomach structure. Each of these increased brain size.
Fossil evidence during that period led to a lot of now extinct names like Australopithecus, homo ergaster (perhaps a predecessor to us), and Neanderthal. The homo sapiens line appeared about 150,000 years ago (heavy on the “about”; literature has a good deal of disagreement.) The Neanderthal million year head start on homo sapiens allowed them to spread all across Eurasia perhaps a million strong. They were actually bigger than the homo sapiens and, like homo erectus, were quite successful, living from 500,000 years ago to about 25,000 years ago. They were strong, used tools, played music, cared for the sick and buried the dead, and may have been religious. In some locations, Neanderthal and homo sapiens shared living space. Cross-breeding probably happened; it seems reasonable to assume that if they could crossbreed, they probably would – sex drive seems to have been a powerful force since the very beginning.
Across the time of homo sapiens first appearance, the earth had a severe drought. Respond and survive was the key; perhaps the extinction of Neanderthal was due to too much dependence on available meat. Homo sapiens survived but the environment was playing serious games. As homo sapiens appeared, climate went through perhaps twenty cycles of very cold then warm temperatures; glaciers built up then withdrew. Global temperatures could vary by 15 to 20 degrees F. in one cycle. This was about a 75,000 year challenge.
Fossil evidence shows homo sapiens migrated out of Africa more than 100,000 years ago; some made it to India and perhaps beyond. Then, as if things were not bad enough, about 74,000 years ago the Toba volcano (in what is now Indonesia) suddenly exploded, causing immense damage as skies darkened with thick debris. Those struggling homo sapiens now had to deal with both truly lousy weather and the smoke and dust blown around from the volcano. Some theories have this disaster wiping out all but a few thousand homo sapiens living in a part of Africa not impacted by the volcano’s damage. Science is not positive if any of that group leaving Africa survived the Toba volcano blast at 74,000 years ago.
These dramatic climate swings obviously impacted the evolution parade. To respond to bitter cold, a specie had to develop better hunting and butchering tools. Most (but not all) scientists feel the inability to respond to the glacial onslaught and cold weather led to Neanderthal extinction. Apparently, about 30,000 years ago as the Neanderthal were nearing extinction, one of those cold periods was particularly harsh.
An important issue science seems to agree on is this: At some time, the number of homo sapiens must have dwindled down to a pretty small number — some say perhaps just a few thousand. This is based on the knowledge that the variation in genes in all humans is actually quite small compared to variations found in other mammals. Some scientists feel such a small group was left because of the Toba volcano; others suggest the reduction was due to harsh weather conditions. Perhaps it was a little of each.
Obviously the remaining homo sapiens group survived and prospered because, 60,000 years ago, they began leaving Africa. This was not a bunch of ignorant, grunting savages. They kept growing intellectually. They used tools, cooked their food, made jewelry, and did elaborate paintings on walls using different colored pigment. They developed spears and bow and arrow for hunting.
The evolutionary story documents steadily increasing complexity. Genders separated, and after that, sought one another. Parenting starts early. As living things begin to live together, behaviors like empathy, cooperating, caring for others, and successfully sharing responsibilities appear. Next week, we’ll explore this complexity a little deeper.