The evolving human body.

Evolution is a slow process, and it may take many generations before a distinct change in a population is apparent, but that does not mean it is not happening. Even now, humans are constantly evolving to better suit their environment. Some past evolutionary characteristics are well known.

Humans living in cold climates tend to have fairer skin to allow for more UV light penetration to facilitate vitamin D production, and short, stocky builds, giving them a reduced surface area to mass ratio that minimises heat loss. On the other hand, humans living in hot climates have thinner, long-limbed builds to allow for greater heat loss, and darker skin to protect against excessive UV light that may cause cancers.

However, lifestyle choices are having increasing influences on which characteristics are retained in populations. For example, the genes allowing adults to break down lactose only emerged about 7,500 years ago in Hungary, where the ability to consume high energy dairy products offered an advantage for surviving cold winters.

In places like East Africa, this change occurred even later, as recently as 3,000 years ago, as cattle farming became more integral to the population’s lives. It makes sense that lifestyle choices would lead to genetic changes associated with food and energy, but what about on more physical structures like bones?

Since around 12,000 years ago, when human society shifted from a forager lifestyle towards agriculture, human skeletons have become increasingly lighter and weaker. This has been attributed to the reduction in physical activity as lifestyles became more settled and sedentary with the rise of technological innovation. As such, there is less need now for the heavy, durable bones that were evolutionarily an advantage for nomadic hunting in the past.

This is where evolution crosses into adaptation. While there are genetic factors linked to bone density and strength, bones are less like rigid, static structures and more like malleable organs that are constantly remodelled to adapt to the mechanical stressors regularly faced.

This results in interesting adaptations in the human skeleton depending on how it is used, and the study of these features is known as osteobiography. One finding was that the enormous, heavy skeletons of ancient inhabitants of Tinian island resulted from a lifetime of stone working and building with huge stone pillars, some weighing nearly 13 tonnes each. Another, in recent years, is the external occipital protuberance that has emerged in many individuals, a spike-like growth at the base of the skull.

It is thought this latest change in skeletal structure is due to the increased use of modern smartphones and tablets. When individuals continuously hunch over their screens, the body compensates for the increased stress of holding up the head by placing more layers of bone.

Environmental conditions, lifestyle choices, these all cause the human body to evolve and adapt for better chance of survival. With more and more technological advancements and changes to our lifestyles, how will humans evolve in the future?