The evolution of human evolution

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Where do humans come from? When you ponder this question, many people will automatically think of two things: firstly, monkeys – due to the widespread belief that humans evolved from apes (we actually evolved simultaneously from a common ancestor); and secondly, Rudolph Zallinger’s March of Progress image, seen above.

Humans have continuously evolved in the 25 million years we’ve lived on this planet. From changing skeletal structures to the development of opposable thumbs, there are many examples for how humans have, and still are, constantly adapting to stay top of the evolutionary food chain.

Need convincing? Here are some recent, modern-day examples for how humans are still evolving to the world we live in:

1. Immune system
Darwin’s theory of evolution famously quotes that the mechanism of natural selection is a result of “the survival of the fittest”. The human immune system is evidence of this, as our bodies continuously fight off diseases without us even realising. The increased prevalence of sickle cell anemia in malaria-stricken areas is, in effect, evolution in action – carrying just one gene coding for the disease provides protection against malaria, increasing the chances of it being passed on in these areas.

2. Wisdom teeth
Due to evolution, our brains have filled our skulls and caused our jaws to narrow – making it hard for our wisdom teeth to come through. The softening of our diets because of the development of agricultural practice has also meant that we don’t need to chew as much or as hard as before. As a result, our jaws aren’t as strong as they used to be and – over time – mutations have surfaced which prevent wisdom teeth from growing at all. In fact, nowadays one in four people are missing at least one wisdom tooth.

3. Blue eyes
Going back 6,000 to 10,000 years you would be hard-pushed to find anybody with light-coloured eyes. This is because the development of blue eyes was caused by a random mutation in the OCA2 gene of a single ancestor. This gene encodes the protein that produces melanin, which gives our eyes their colour. Because of this mutation, the ability to produce brown eyes was effectively turned off, meaning that melanin production was reduced and the eye colour transformed from brown to blue. As time moved on, this mutation passed from generation to generation and the number of blue-eyed people in the world rapidly increased.

4. Smaller brains
Over the past 20,000 years, male brains have reduced by an amount equivalent in density and size to a tennis ball. However, that doesn’t necessarily mean that we aren’t as clever as we used to be – in fact, scientists believe that smaller brains have developed in humans simply because we rely on society to get by nowadays and no longer need as much individual brain space as our ancestors did.

These are just a few examples, but there are numerous others that prove why we have evolution to thank for our continued survival on this planet. Adaptation may be a slow process but, with the emergence of the technological and inter-connected world that we live in, it looks like Rudolph Zallinger’s famous image could soon be in need of an update.

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