For over 50 years, British-born palaeoanthropologist Meave Leakey has been unearthing fossils of our early ancestors in Kenya’s Turkana Basin. Her discoveries have changed how we think about our origins. Instead of a tidy ape-to-human progression, her work suggests different pre-human species living simultaneously. Leakey’s new memoir, The Sediments of Time: My Lifelong Search for the Past, co-written with her daughter Samira, reflects on her life in science and pieces together what we now understand about the climate-driven evolution of our species. Leakey is part of a famous family of palaeoanthropologists. Her husband, Richard Leakey, and his parents, Louis and Mary, are known for their discoveries of early hominins. Meave, 78, is a professor at Stony Brook University, New York and director of field research at the nonprofit Turkana Basin Institute, a collaboration between the Leakey family and Stony Brook. You graduated in the 1960s with a degree in zoology and marine zoology from the University of Bangor and envisaged a career as a marine biologist. How did you end up fossil hunting in Africa? I had written to many marine centres around the world and got the same answer: they didn’t have facilities for a woman on a boat. Fed up, I decided I would have to try something else. A boyfriend at the time found an advert on the back page of the Times for a research position at the Tigoni Primate Research Centre in Kenya. I phoned the number and Louis Leakey picked up. Within weeks I was on the plane. I met Richard when I was running the centre. I had just got my PhD in zoology, studying monkey skeletons. Richard contacted me to talk about how the centre was spending too much money and we needed to make savings. We hit it off and I began to see him quite a bit. He asked if I would like to come and work with him at his fossil site. That’s how I got to Turkana and on to fossils. You and Richard got married in 1970 and your daughters, Louise and Samira, were born in 1972 and 1974. How did you balance research and motherhood? I had no wish to miss the excitement of fieldwork, so both children were hauled off to Turkana within weeks of their birth. They would stay in the base camp with somebody to look after them while we went out and worked. As they got older they would come out with us occasionally. There is a particular skull which remains one of my favourite fossils ever, because of the happy memories I have of reconstructing it, with a baby hippo playing in the lake and baby Louise playing at my feet in a cool basin of water. It was a really special time. In the late 1980s, Richard went to head the Kenya Wildlife Service and you took over leading the fieldwork. In 1999 your team found the skull of an early hominin that was roughly the same age as the famous Lucy (Australopithecus afarensis), the 3.2m-year-old fossil skeleton discovered in 1974 in Ethiopia. You called it Kenyanthropus platyops: the flat-faced man from Kenya. How did that change our understanding of evolution? Lucy got a huge amount of publicity. She was always projected as the common ancestor of humans. I always felt that it didn’t make sense, because if you looked at any other animal lineage there were always so many species. I thought: there has to be diversity [in the early hominins]. When we found this specimen, it was crushed and broken, so it took a long time to make sense out of it. But you could tell it was something completely new, and different from Lucy. It was living contemporaneously with Lucy, but had this really flat face. The significance was far reaching: it showed Lucy was not necessarily the ancestor of all later hominins. Your book doesn’t include a family tree of our origins. Was that deliberate? Yes. I tend to not try and draw straight lines between things. There remains so much more to be discovered. I worry that rather than adding to our understanding, the building of lineages can only be preliminary and can, in fact, be misleading. There are periodic attempts to debunk Africa as the ‘birthplace of humankind’. How have things changed over your career? And should east Africa or southern Africa, where early hominin fossils have also been found in caves, get the moniker? Early palaeontologists didn’t believe that humans could have come from Africa. There was a prejudiced insistence that humans must have originated in Europe. The work to convince the scientific community and the world otherwise was started by my parents-in-law and continued by my husband, myself and my daughter Louise. As I have gone through my career it has become more and more accepted. Definitely Africa is where it all began. The climate and the vegetation were right. And, for me, east Africa is most likely, because if you look at where nonhuman primates are distributed today, they concentrate around the tropics and the equator. How did we evolve our tremendous brain power and our ability to walk on two legs? Evolution happens because of changing habitats driven by changing climate. Driven by a drying trend, towards more open savannah, I suspect our ancestors started coming down out of the trees to the ground. They found if they stood on two legs they could reach food – like berries and fruits on bushes – better, and they could travel further. Big brains came later, after bipedalism and increased dexterity. Brains are expensive in terms of calories. To develop a big brain, you have to have a good source of food. When our ancestors started finding a way to hunt and catch a lot of meat, they were able to evolve bigger brains. You donated a kidney to Richard, and helped him through losing both his legs in a plane crash. Do you think our ancestors formed similar social bonds? I am sure. We found a 1.6m-year-old femur [thigh bone] that was very clearly broken and mended, and that can only have meant the individual being cared for. Otherwise, they wouldn’t have made it. The degree of social bonding must have been considerable. Do you still go on digs, and what would your ultimate find be? I do still go into the field, but not as much. Louise and I have an amazing crew, so we don’t have to be there all the time. We are primarily working on the west side of Lake Turkana, going over 4m-year-old sites we worked decades ago. Fossils are weathering out all the time, so you can find a whole lot more. Finding a complete skeleton of any early hominin is my dream. We can learn so much more than from a skull alone. Are we still evolving? I don’t think we’re still evolving physically, because we control our environment so much. And while there is climate change now – which is going to mean that we cannot live in places that we live today – it is hard to imagine it will affect our physical evolution because of that control. Our technology is evolving fantastically, though. Our evolution now is more technological than morphological.