We teach, tell stories, trade. We have morals, laws. The details of our tools, fashions, families, morals and mythologies vary from tribe to tribe and culture to culture, but all living humans show these behaviours. That suggests these behaviours — or at least, the capacity for them — are innate. These shared behaviours unite all people. We inherited our humanity from peoples in southern Africa , years ago. Archaeology and biology may seem to disagree, but they actually tell different parts of the human story.
Bones and DNA tell us about brain evolution, our hardware. Tools reflect brainpower, but also culture, our hardware and software. Humans in ancient times lacked smartphones and spaceflight, but we know from studying philosophers such as Buddha and Aristotle that they were just as clever. That creates a puzzle. If Pleistocene hunter-gatherers were as smart as us, why did culture remain so primitive for so long?
Why did we need hundreds of millennia to invent bows, sewing needles, boats? And what changed? Probably several things. First, we journeyed out of Africa , occupying more of the planet. There were then simply more humans to invent, increasing the odds of a prehistoric Steve Jobs or Leonardo da Vinci.
We also faced new environments in the Middle East, the Arctic, India, Indonesia, with unique climates, foods and dangers, including other human species. Survival demanded innovation.
Many of these new lands were far more habitable than the Kalahari or the Congo. Climates were milder, but Homo sapiens also left behind African diseases and parasites.
That let tribes grow larger, and larger tribes meant more heads to innovate and remember ideas, more manpower, and better ability to specialise. Around 90, years ago, these humans started making tools to catch fish. Then, around 12, years ago, humans began to grow food and change their surroundings in order to survive and eat. As food became more sustainable, and living became easier, humans began to produce more.
As humans developed and grew, their bodies changed. Their brains became bigger, which helped them to develop new tools, including language. They changed the world around them to better survive harsh and changeable weather. Over time, these humans created civilizations and became what we know as humans now. This may be because human populations became smaller as they spread out from their original settlements in Africa and so genetic diversity within these populations was less.
As a result the scientists stated that modern humans could not have emerged in different places, but instead had to have come from one region, Africa. These were found in in Omo National Park in south-western Ethiopia. The skulls have been dated to , years ago, highlighting how humans have evolved relatively recently. Evidence shows that the first wave of humans to move out of Africa did not have too much success on their travels. At times it appears they were on the brink of extinction, dwindling to as few as 10, The eruption of a super volcano, Mount Toba, in Sumatra 70, years ago may have led to a 'nuclear winter', followed by a 1,year ice age.
This sort of event would have put immense pressure on humans. It may be that humans were only able to survive these extreme conditions through cooperating with each other. This may have led to the formation of close family groups or tribes and the development of some of the modern human behaviours we are familiar with today, such as cooperation.
Between 80, and 50, years ago another wave of humans migrated out of Africa. Due to their newly cooperative behaviour they were more successful at surviving and covered the whole world in a relatively short period of time. As they migrated they would have encountered earlier, primitive humans, eventually replacing them.
A map showing human migration out of Africa. Image credit: Genome Research Limited. Homo neanderthalis , or Neanderthals as they are more often known, are an extinct species of human that was widely distributed in ice-age Europe and Western Asia between , and 28, years ago.
They were characterised as having a receding forehead and prominent brow ridges. Since then, researchers have been striving to uncover the position of Homo neanderthalis in modern human evolution.
Homo neanderthalis appeared in Europe about , years ago and spread into the Near East and Central Asia. They disappeared from the fossil record about 28, years ago. Their disappearance has been put down to competition from modern humans, who expanded out of Africa at least , years ago ,year-old remains of modern humans have been found in Israel , suggesting that there would have been a period of co-existence.
Did the two species interbreed? Have Neanderthal genes therefore contributed to the modern human genome? Initial studies of DNA from the mitochondria of Neanderthals showed that their mitochondrial DNA looks quite different to that of modern humans, suggesting that Homo neanderthalis and Homo sapiens did not interbreed. They also identified another archaic human group called 'Denisovan', named after the Siberian cave in which the fossil finger, from which the DNA was obtained, was discovered.
In they obtained a more refined Neanderthal genome sequence from a 50,year-old Neanderthal toe bone, found in the same cave in southern Siberia. The genome sequence suggested that early modern non-African humans interbred with their now extinct ancient human cousins. DNA can survive in bone long after an animal dies. Over time the DNA from various microbes that encounter the skeleton will also invade the bone.
Scientists therefore have to ensure that they sequence only the Neanderthal genome and get rid of any DNA material left behind by these microbes or resulting from contamination by modern humans who handle these bones. As with the human genome sequence, the Denisovan and Neanderthal genome sequences were made available online for free.
The genome sequence suggested that early modern non-African humans interbred with their now extinct ancient human cousins as they journeyed along coastlines and over mountains.
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