Our species, Homo sapiens, is ridiculously young. We have only existed for a fifth of a million years. In that time we have expanded from our African birthplace to reach every continent, and even outer space. Our activities have precipitated the sixth mass extinction and unleashed the fastest episode of climate change in Earth’s history. Yet we are also the only species that has ever managed to piece together the history of Earth.
Almost immediately after the dinosaurs were wiped out, mammals evolved the ability to nourish their young inside their wombs using a placenta, just like modern humans. Soon, some of these early placental mammals evolved into the first primates. They would ultimately give rise to monkeys, apes and humans. But the first ones were small creatures. The oldest known primate skeleton is of a species called Archicebus achilles, which weighed no more than 30 grams. They lived in the hot and humid rainforests of Asia.
Our brains consist of cells which conduct nerve impulses through electrical and chemical signals, these are called neurons. Neurons do not fire at all times; however, that does not mean that inactive neurons are useless, nor that 90% of the 86 billion neurons that make up the human nervous system are permanently inactive.
Your saliva contains an enzyme called amylase, made by the AMY1 gene, which digests starch. Modern humans whose ancestors were farmers have more copies of AMY1 than people whose ancestors stayed as hunter-gatherers. This digestive boost may have helped start farming, settled villages and modern societies.
Nobody knows when our ancestors learned to control fire. The oldest direct evidence comes from Wonderwerk Cave in South Africa, which contains ashes and burned bones from 1 million years ago. But there is evidence hominins were processing food even earlier, and that might have included cooking with fire.
Our oldest ape-like ancestors mostly ate fruit, but later species like Australopithecus branched out. As well as eating a wider range of plants, such as grasses, they seem to have eaten a lot more meat, and even butchered it with stone tools. More meat meant more calories, and less time spent chewing.
Our hands are unusually dextrous, allowing us to make beautiful stone tools and write words. That might be partly down to a bit of DNA called HACNS1, which has evolved rapidly since our ancestors split from the ancestors of chimps. We don’t know what HACNS1 does, but it is active in our arms and hands as they develop.