It certainly feels more apt, given that humanity has become so totally dominant over the immediate fate of life on Earth that we are not merely the ultimate apex predator, but we have created our very own geological age, the Anthropocene.
It’s worth reflecting again on this dominance. Humans now constitute 30 per cent of the planet’s land mammal biomass and the livestock which forms our diet is a further 67 per cent, leaving just three per cent for wildlife. We have deliberately emitted enough carbon into the atmosphere to drive concentrations to a level not seen in over 800,000 years. We have completely revolutionised the natural nitrogen cycle, and become the decider of which other species survive, and which meet their doom. It’s an astounding level of power to have in the hands of what was once a slow, physically weak, peculiarly large-headed ape huddling in a remote corner of East Africa.
“So how on Earth did we do this? How did we turbo-power our way to the very top of the food chain, and essentially out of the natural world entirely? To answer this question, Maslin takes us back to the very beginning, the Big Bang”
What follows is a quick-fire crash course in the history of the universe, our solar system, and the formation of our planet, before we land in the East Africa Rift Valley, a 4,500km tectonic rift stretching from Syria to Mozambique, which has been steadily ripping Africa apart for tens of millions of years. This is where Homo sapiens were born. From here, we eventually conquered the world.
In order to properly explain how the multi-layered factors at play in this region determined human evolution – through the stages of bipedalism, the emergence of various other hominins such as Sahelanthropus tchadensis and Homo erectus, before finally Homo sapiens arrived – we need to understand the interplay between global climates and tectonic activity. This is where Maslin delivers far more than he promises. An anticipated story about human evolution takes a rapid journey through plate tectonics, glacial and interglacial climate cycles, deep ocean circulations, orbital forcing and more. This impressively in-depth and well-explained mix of encyclopaedic information explains how changing atmospheric circulations and tectonic activity in the Rift Valley led to a fluctuating climate, alternating between aridity and high rainfall (with increased numbers of large lakes) and therefore increasing biotic diversity. As he writes: ‘It is unsurprising that the tropics are a hotbed of evolution, because even if there were no major climate changes, the whole region undergoes massive hydrological shifts every 5,500, 11,000, and 21,000 years.’
There is an amazing amount of information packed into this surprisingly slim book. Maslin is able to quickly fill us in with the basic information on highly complex global processes we need to know, before continually returning us to the core theme of how this led to who we are today. Snazzy graphics – diagrams and graphs – helps break up the flow of information being directed our way, and aide smooth digestion.
It’s notable that for all we do know about human evolution, such as the existence of other hominin species, or the paths we took out of Africa, there are still huge gaps in our knowledge. Why did Homo sapiens emerge 200,00 years ago? Why did we sit around for 150,000 years not doing much, before suddenly exploding in number around the world? How did we develop language, that essential tool which enables our species to live together peacefully, and pass on skills through social groups and generations? Maslin applies his own mind to existing theories and creates a hybridised narrative, one based on the mix of local, regional, continental and planetary changes which have affected East Africa over millions of years. He powerfully illustrates why nexus thinking of geography’s broad disciplines is so key to fully understanding such an immense subject as the evolution of humanity – the story of us.