If you have stuck with this series, about 3.5 billion years ago blue green algae dominated the earth. It built stromatolite reefs to rival the GBR for 3 billion years and the same blue green algae species still survive today. By comparison humans are nothing… not yet. When we talk human evolution we often focus blindly on people anatomically identical to homo sapiens. Humans have been around for longer than that and there have been lots of versions. Primates diverged from other mammals about 85M years ago, although we have only found fossils from 55MYA. Lots of primate species diverged and died out, but chimps and hominids split from gorillas about 8MYA, basically yesterday in geological time. Chimps stayed at home in Africa and have survived OK pretty much unchanged. Hominids took a chance and became nomads and have had a bumpy ride. This bumpy ride forced them to evolve new strategies and biological adaptations. Homo habilis appeared 2.8MYA and was probably using stone tools. This didn’t stop them from becoming extinct. Another start was made with Home erectus and Homo ergaster. H.ergaster was an upgraded model with twice the brain size. At the geological equivalent of 9.30 this morning (about 1.8MYA), Homo ergaster managed to leave the tough conditions of Africa and spread to Asia and Europe. Homo ergaster was a reasonable success, lasting about 500,000 years and spawning 4 other refinements of the type. Right now in geological time (50-100 thousand years ago) very primitive forms of Homo sapiens walked out of Africa. Modern DNA study shows that we interbred in a limited way with other human species such as Neanderthals, and they contributed about 6% to our current genome. So the expression, “the boss is a bit of a Neanderthal” is scientifically true. Neanderthals were a cold climate European adaptation that lasted about 150,000 years until the climate was no longer cold, and ‘warm weather’ versions of humans flourished instead. Homo sapiens are presently less successful than H. Ergaster or Neanderthals in terms of long-term survivability of the type. We are very numerous, but are still the ‘new kids on the block’ and have yet to prove we can evolve useful long-tem adaptations. We need to ride through several abrupt changes in climate and other challenges over the next few millions of years before we can truly be considered a “survivor” species. If the width of an A4 page is the history of evolution, homo sapiens have been around for about 1/400,000th of a millimetre, you couldn’t draw it or see it. So far, we don’t even add up to a blip on the evolutionary radar. The only odd thing about Homo sapiens is that they became the apex predator very rapidly. We are an animal that has no savage teeth or claws and don’t even have enough fur to keep warm (well mostly). We look basically helpless and easy meat for any sabre toothed tiger. 12 Homo sapiens have opposable thumbs and can make snazzy tools which helps, but earlier versions of human 1.0 had toolmaking ability and even chimps can make simple tools. Humans can band together to act as a team, but so can hunting dogs. We can alter the landscape, but if that was the key issue we should be struggling for supremacy with beavers. The trick must be the brain. It is big compared to all other primates. That can’t help you when confronted with a sabre tooth tiger, but you can use it to visualise a world without that threat. You can then build tools, form tactics, alter the landscape, and drive sabre tooths to extinction and win the oldest battle on earth, competition between species. Everyone has a theory about human superiority, but mine is that we can think outside the square, visualise a truly abstract goal we want to reach, find meaning in a Jackson Pollock squiggle. We can expand our numbers by not only excluding competing species, but by using other species like dogs and cattle in new mutualistic relationships to spread us and these other species across the planet. The fact that we can also drive around in cars, build nuclear reactors, and reach the moon, are mere refinements. There have been arguably 6 major extinction level events in geological time. The most severe occurred at the end of the Permian period when 96% of all species perished due to climate related events. An asteroid induced climate change saw the end of the dinosaurs in the K-T event (50% species loss). The Ordovician-Silurian mass extinction was the third largest and mostly killed marine species. The late Devonian extinction hammered life in the shallow seas. During the final 18 million years of the Triassic period, there were two or three phases of extinction. The last extinction event is the Holocene extinction and we are living in it. It is caused mostly by the ascent of humans. It is a name proposed to explain what will be the next big set of entries into the ‘exists as a fossil only’ ledger. There are 875 documented extinctions since 1500, but that is not even part of the story. Undocumented extinctions are a lot higher. One source claims as many as 140,000 species per annum, most in recent times. The extinctions are now reaching into hardier species like plants for the first time. It is believed that about 7% of all species have already become extinct, many just in the few decades of the post-war period. It is still a long way off one of the really big prehistoric climate induced extinction level events. To duplicate that we’d have to do something really dumb like artificially fill the atmosphere with millions of years worth of stored carbon. Surely with that big visualising brain we would realise what’s coming and not be that self-destructive? If that happens, our legacy will become a very thin black carbonised line in some fossiled sediments. The lemurs that might evolve to follow us will have to spend their grant money speculating about what caused it. Nothing can live forever, the sun’s fuel cycle is already winding down and in a mere one billion years it will be so hot it boils off our oceans. The earth will become a lifeless rock for a further 4 billion years before it is consumed by the red giant that use to be our sun. In that sense we are already 80% through the history of evolution. Time is running out, so now we have largely tackled the scourges of famine, disease and letterbox junk mail, it might be time to use those brains and speculate on the kind of legacy we could have in a billion years time…if we truly decide to visualise getting only one third as far on the evolutionary scale as dumb blue green algae.