Humans: Journey to Homo Sapiens

Plato once defined humans as being featherless bipeds. Diogenes the Cynic replied by plucking a chicken and metaphorically shoving it in Plato’s face, shouting ‘behold a man!’. Needless to say, the definition did change slightly afterwards: to featherless bipeds with broad flat nails.

I’m sure it is no secret that we have evolved from apes, but in this article I’m going to take a closer look at what this really means and how we have come to be the globe-dominating species we know today.

Humans are in the order primates, which contains other familiar faces such as lemurs, monkeys and apes. Primates as we know them today started to appear around 60 million years ago; by about 20 million years ago, all the branches of the tree of life that lead to modern day primates had been established.

Most primates are tree dwellers, and the challenges this lifestyle brings have lead to the development of some defining human characteristics. Our ancestors’ limbs started to elongate, and they developed prehensile hands, capable of grasping onto tree branches. Eyes moved more forward in the head to help with depth perception, helpful when swinging through the canopies at a height where one slip could be lethal. Our closest relatives in the primate world are chimpanzees, but the last common ancestor we had with chimps lived about 6 or 7 million years ago, so what has happened in the meantime?

The theory is that around 3.5 to 4 million years ago, the first human-like ancestors started to walk upright around the grasslands of eastern and southern Africa. These first humans were only about 1 to 1.5 metres tall and were classified under the genus Australopithecus. The first specimen, found in a desert in northern Ethiopia in 1974, came to be known as ‘Lucy’ (what a great name by the way).

Australopithecus afarensis would eventually evolve to give the branch Homo habilis. Then came Homo erectus, about 1.5 million years ago. Specimens of this species have been found to vary wildly in age from 1.5 million years to as recent as 200,000 years old. They seemed to thrive for a long time, but many were killed off in an ice age. Those that did survive would evolve to become modern-day Homo sapiens.

Where do Neanderthals fit into the picture? They lived from about 400,000 to about 40,000 years ago, and we coexisted with them for a large percentage of that time. They had large sloping foreheads, furrowed brows and smaller chins, but eventually scientists realised that their bodies were very similar to Homo sapiens. They even used to leave flowers on their loved one’s graves.

Neanderthals and Homo sapiens diverged about 250,000 years ago and Neanderthals eventually diminished as Homo sapiens began to rise in prevalence. Where did they go? Scientists think they died out, but it is also likely that some interbred with Homo sapiens.

So, what makes us humans so special? Are we really just featherless bipeds? Apart from all the philosophical, psychological and ethical answers to this questions (which to get into would be to open another can of worms entirely), we humans have developed a bipedal gait from our upright posture and opposable thumbs. These traits on their own aren’t special and can be seen in other primates; what sets us apart is our ability to make use of these generalist traits to our advantage in whatever situation we are in.

The development of our thumbs has allowed humans to have much greater manual dexterity and ability to manipulate our surroundings, but without our brains also evolving, opposable thumbs would have been pointless. If there is one thing that humans excel at, it’s adaptability.

We have dispensed with the learned genetic traits that many other species have from birth, resulting in rather hapless young that can’t particularly defend for themselves. This allows a child to learn about their surroundings and specifically develop to live in those conditions. That’s pretty unique in the animal kingdom and that’s what makes us human. We can survive in the toughest Antarctic tundra, arid deserts and even when chucking ourselves into space: because we are the best generalists.