We often think of human evolution as something disconnected from us. Large anatomical changes that happened in the distant past. However, it also made many changes to the way your body operates. Physiological tweaks which - whilst small in scale - continue to influence us to this day.
It's understandable these changes don't leap to mind when we think about human evolution. These are tweaks to our underlying biology. This has long since rotted away by the time we get our hands on our ancestors. However, an in-depth comparison with extant primates has identified the ancient human physiology. Based on this, researchers have examined what physiological changes have evolved since then.
It turns out that there's been a lot of change. The biology behind many of everyday activities - from eating to running - has developed a unique human twist over the course of our evolution.
Super-endurance
Chimps travel a few hundred meters an hour. As you probably know from experience, humans move about a bit more than that. Now, this isn't just because chimps are lazy (although that might explain why they have yet to rise up against us). Evolutionary changes have given us a lot more endurance than our ape relatives.
Part of this comes from anatomical changes. We have elasticated arches and tendons (such as the Achilles) in our foot. This conserves energy between steps, making the whole process more efficient. However, evolution has also granted us a physiological superpower. The number of cells in our blood has decreased dramatically. That means more red blood cells transporting more oxygen around our body. By keeping our body well supplied we have the endurance needed to outpace chimps.
This obsession with movement does more than keep Fitbit in business. It's the reason humans are successful. The fact that chimps don't move much limits where they can live. They need to be where food is within reach. This is why they're only found in the rainforest, where their favourite fruit is everywhere. But if try and migrate elsewhere bad things happen. Food is so far apart and they have to travel such distances that their inefficient locomotion, combined with their fur, means they would overheat before they could feed.
The researchers behind this discovery also speculate our super-blood might be linked to endurance running. Thanks to it we can run further than any animal. Some hunter-gatherers put this to use when they hunt, tiring out their prey until it's an easy kill. However, w hether this played a big role in human evolution is debated.
Disease resistance
Thanks to that super power humans were able to spread out from the tropical limits of chimps. These strange new lands held strange new diseases for us. Our immune system had to evolve to cope. And it had a little help in the process.
As most of you probably know, we interbred with many of the human species that came before us. The Neanderthals are perhaps the most famous example. Many of the genes we inherited from this romp still persist. They give us an advantage, so natural selection ensured they stuck around until the present day. The list of such genes is fairly long and influences many aspects of our body. From our skin to our immune system.
Thanks to the Neanderthals - and our own adaptations to these strange environments - we have an immune system not to be trifled with. Key physiological changes include white blood cells that mature faster, along with a greater overall number of white blood cells.
Nowadays these abilities are even more important. We've created a society almost designed to give doctors a hard time. We live in huge, close-knit populations sharing all sorts of germs between us. And if that wasn't bad enough, we've brought animals into the mix. There's a reason all the scariest diseases involve animals. Swine flu was a big deal because our farming-based society allowed it to become a big deal.
As an interesting caveat, the review of our physiology found not every aspect of our immune system had undergone some evolution. The researchers could not figure out why some parts remained the same. As such, they caution about making too far-reaching implications about how great our immune system is. Beyond the fact it is a definite upgrade when compared to chimps.
Physiological non-noms
Of course, there's a reason we live close with animals. It isn't to just keep doctors in a job. We now live in a farming-based society, so we can get food without trecking for miles a day. It comes with some downsides, like all that disease. But the benefits are enough to make it worthwhile.
However, farmed food is a bit different to what we traditionally ate. As any palaeo-diet enthusiast would tell you, we evolve to eat large quantities of meat. So they eat the most prehistoric of foods: cow.
Whilst they may have a silly way of showing it, they are onto something. The human diet has undergone some fairly major changes. Fortunately, evolution has equipped us with a body that can deal with it. Mutations have increased our production of amalyse, which helps us break down the starchy foods which now dominate our diet. The fact you can eat large amounts of potatoes, rice, pasta, wheat, and more without suffering from crippling intestinal problems is all thanks to evolution.
These physiological changes may pre-date farming. Hunter-gatherers also switched to a much starchier diet than chimps have. As we moved further north, fruit no longer became a viable food source. We had to supplement it with roots and tubers. Accordingly, modern hunter-gatherer populations show that same spike in amalyse production farmers have. Our starch digestion might be an ancient superpower that made farming viable.
Conclusion
On most days you probably do some walking, don't get riddled with disease, and eat a bit of starch. These seemingly simple activities are only made possible by generations of evolution. It's equipped you with physiological superpowers that makes apes jealous. And humans successful.
References
Dávid-Barrett, T. and Dunbar, R.I., 2016. Bipedality and hair loss in human evolution revisited: The impact of altitude and activity scheduling. Journal of human evolution, 94, pp.72-82.
Lehmann, J. and Boesch, C., 2004. To fission or to fusion: effects of community size on wild chimpanzee (Pan troglodytes verus) social organisation. Behavioral Ecology and Sociobiology, 56(3), pp.207-216.
Perry, G.H., Dominy, N.J., Claw, K.G., Lee, A.S., Fiegler, H., Redon, R., Werner, J., Villanea, F.A., Mountain, J.L., Misra, R. and Carter, N.P., 2007. Diet and the evolution of human amylase gene copy number variation. Nature genetics, 39(10), pp.1256-1260.
Schulkin, J., 2016. Evolutionary Basis of Human Running and Its Impact on Neural Function. Frontiers in Systems Neuroscience, 10.
Vining, A.Q. and Nunn, C.L., 2016. Evolutionary change in physiological phenotypes along the human lineage. Evolution, Medicine, and Public Health, 2016(1), pp.312-324.
