Origins of Us: S01E01: Bones

6 Million years ago in an ancient African forest we meet Chimpanzees. We’re genetically close to Chimpanzees – but, Alice explains, we’re not related to them. This means that we haven’t evolved from them. But we can go back to a time 6 million years ago, the ancestors of the Chimpanzees remained in the forest, while ours, headed out – into different habitats.


Chimpanzees have very long arms and have grabbing feet with their big toes further out – with the ability to grasp branches. This is something that we’ve lost. To replace this, we have long legs, for walking. But what triggered this? And when?

We then meet Toumai. The differences between this skull and a Chimpanzee are that the Toumai spinal cord comes out directly below the skull, the Chimpanzee spinal cord comes out the back at an angle. This shows that Toumai was bipedal. We then look at the human spine, seeing that the lumbar region has massive vertebrae to cope with the weight of the body. But the discs wear away and the lumbar region is the biggest reason of back complaints. So why did we begin to walk upright if it causes so many problems?

Alice explains that the process from climber to walker was a slow process, that it’s hard to pin point when then change really occurred. There is a big clue in Dorsal Flexion. The angle at which we can point our feet towards our shins. For us, we don’t have much dorsal flex – for Chimpanzees it’s a lot. So much that they can literally have the sole of their feet on the truck of a tree while climbing up it!


2 million years ago, with Lucy, one of the very famous finds, we see that the ankle of ancestral humans already had the signs of a walker. The tibia joint to the foot for climbers is trapezoid. The same place in us Human walkers it square – as it was with Lucy. So although she looked more like an ape than a Human, she was paving the way for us and our bipedal fashion. This suggests that they were exploring – moving beyond the confines of the forest.

Every step involves the coordination of 200 muscles. As we grow and begin to walk, our bones change. We don’t know how much this is due to pre-programming and how much is due to our impulse to walk. What we do know is that it look millions of years for our ancestors to master standing and walking.


A big driver for walking was the change of climate that brought grasslands such as the Savannah. This saw an influx of new Hominids, with only 1 eventually surviving. Hominids didn’t just survive though, they thrived. A skeleton of 1.5 million years ago, that of ‘Nariokotome boy’ shows long leg bones. But it also shows big knees and hips with a narrow waist along with a ligament attachment in the skull. These are signs that the body is trying to stabilise the trunk, something we apparently don’t need for walking. So why did this skeleton need stabilising?

We find that it’s because nariokotome boy was running. When we run we’re much less stable, which is where our long narrow waist comes in. It allows us to twist as we run. We also have a ligament that attaches to our skull, this stops our head pitching forward as we run, and this is the nuchal ligament. The gluteus maximus also comes into play when running, without it, we couldn’t run. We are endurance runners, that’s the body that was given to us by our ancestors, as it was essential to our survival. It means that we could compete with other scavengers for meat and hunt prey over long distances, sometimes known as persistence hunting.

Another adaptation that was developed for our new bipedal way, especially our running. This meant that we needed to lose our fur – so that the heat could be evaporated effectively.


2 million years elapsed between Toumai and nariokotome boy. 2 millions years between being climbers and walkers. The first stone toolmaker, as far as we currently know, was Homo Habilis around 2 million years ago. We see Alice with some Chimpanzees, watching the termite fishing. We see that they hold the rod in a different way to us. Us between thumb and fore finger and the Chimpanzees with their whole hand – a less dexterous way. But why, when we have the same bones and the same muscles, do we choose to hold tools in a different way to the Chimpanzees?

This is due to a larger thumb that evolved around 2 million years ago, with Homo Habilis. In comparison the Chimpanzee thumb is quite small and weak. This big thumbs seems to be important, not when making tools, but actually when using them. The pressure of the thumb is much higher than with the fingers when using tools, for instance when cutting with a knife.

This all goes to show that our bones developed as our habits, not just our habitat, changed. Our creativity, not just our surroundings lead to this evolution.



Without this, Homo Sapiens, could never have been so successful. Sometimes it seems that our creativity to alter the world around us is limitless. Especially with the virtual worlds we are now creating online. I wonder what adaptations this will lead to. Only time will tell.