At present, humans are the most complex and advanced species on the planet. It is hard to believe that our ancestors had more in common with squirrels than modern humans. Yet, it is true. Our evolutionary history dates back to the time when an asteroid wiped out the dinosaurs 66 million years ago. This catastrophic event allowed a new class of animals to rise, and the mammals became the dominating class. Between three and five thousand species of mammals emerged within the next ten million years, including the earliest classes of whales, bats, rodents, and monkey-like primates.
The prehistoric primates went through many changes very quickly. Around 60 million years ago, the evolutionary line divided into strepsirrhines and haplorrhines, the wet-nosed and dry-nosed primates, respectively. The haplorrhines, which developed larger brains, relied on their vision and were primarily diurnal, showing two more human-like attributes. They continued to diverge for millions of years, and several of our primate cousins branched off the family tree.
Proconsul and the Emergence of Ape-Like Primates
Around twenty million years ago, the first ape, known as Proconsul, arrived. The earliest apes began taking on physical attributes that were increasingly human-like. They were significantly larger than their ancestors, weighing up to 110 pounds, and notably lacked a tail. The apes continued to vary, branching into the Great and Lesser Apes and giving birth to some of our other evolutionary cousins, such as gibbons, orangutans, and gorillas.
Our closest cousins, the chimpanzees and bonobos, arrived much later around seven million years ago. However, one of the first big steps in our transcendence from ape to human came with the evolution of the Ardipithecus, the first genuinely bipedal genus. They still remained a primarily tree-climbing species but developed the breakthrough ability to walk on two legs, making them more adjusted to walking reliably, which freed their hands for the earliest known use of stone tools.
The Ardipithecus evolved into the Australopithecus around two million years ago. Australopithecus retained apelike features but was becoming significantly more human still. The opposable big toes present in earlier species moved to face forward on their feet, allowing them to walk reliably, which freed their hands for the earliest known use of stone tools.
The Emergence of Genus Homo: The Triumph of Larger Brains Over Stronger Jaws
Around two million years ago, evolution evolved along two more distinct directions. While one group is said to have developed stronger jaws to better help them to eat the nuts and vegetation specifically available at that time, another evolved with weaker jaws but larger brains. While both branches survived for a significant period, those with the larger brain proved to be more adaptable in the long run and ultimately gave rise to the genus Homo, taken from the Latin for man.
The first member of the Homo genus was Homo habilis, colloquially known as “Handy Man.” Homo habilis had ever-widening use of tools, which led to many major evolutionary advancements happening quickly. Within just 500,000 years, Homo habilis had given rise to another new classification, Homo erectus, making possibly the most crucial evolutionary leap toward modern man.
Homo erectus closely resembled the proportions of a current human body. They had relatively elongated legs and shorter arms compared to the size of their torso, which was the result of their being fully adapted to living on the ground. Homo erectus had a slightly larger brain size, although it was still only about 60% the size of a modern human’s. They were the first to use fire as a tool, which along with their bipedalism, enabled them to migrate outside of Africa, becoming the first group to be widespread across Europe, Asia, and Africa. Homo erectus also cared for their old and weak, something that was virtually unheard of until this point, suggesting emotional and social development alongside their physical evolution.
The Intricate Evolutionary Web of the Homo Genus: Divergence, Cross-overs, and Origins
Over the period between 1.9 million years ago and 100,000 years ago, and as a result of Homo erectus’ migratory patterns, new members of the Homo genus began springing up all across the world map. As each new species evolved to adapt to different environments, these various human groups began to diverge and cross over at various historical points, causing an intricate web of evolutionary lines. While it is difficult to precisely know from which line after Homo erectus we (modern humans) find our origins, we do know that we were neither the first nor the last species to evolve along our branch.
First appearing around 300,000 years ago, Homo sapiens are distinguishable from other Homo groups most significantly by their having much larger brains, an adapted skull shape to house those larger brains, and a lighter skeletal frame. As a result, ancient Homo sapiens were an exceptionally innovative group, developing advanced tools like fishhooks for hunting, bows, arrows and spears (also for hunting), sewing needles (for clothing), and various building materials and methods (for shelter). This ensured that sapiens would outlast all other Homo types, with the last Neanderthal dying out about 40,000 years ago.
But, while that’s the human story so far, evolution is far from being done. As much as we tend to assume that we’re the ultimate, end-of-the-line model, it will continue to alter us well into the future. In the past 100,000 years, for example, the average height of Homo sapiens is thought to have shrunk slightly, although we do appear to have grown slightly taller in just the past couple of centuries. Meanwhile, although brains had been getting progressively larger throughout evolution up until this point, ours have actually decreased in size over the past 30,000 years or so, with it commonly said that a modern human has lost about a tennis ball’s worth of brain size compared to earlier sapiens.
In conclusion, human beings have come a long way since the time when our ancestors had more in common with squirrels than modern humans. Our evolutionary history dates back to the time when an asteroid wiped out the dinosaurs 66 million years ago, allowing a new class of animals to rise, and the mammals became the dominating class. Between three and five thousand species of mammals emerged within the next ten million years, including the earliest classes of whales, bats, rodents, and monkey-like primates.
Our evolutionary journey continued with the prehistoric primates, the Ardipithecus, the Australopithecus, Homo habilis, and Homo erectus. Homo erectus made the most crucial evolutionary leap toward modern man, and various human groups began to diverge and cross over at various historical points, causing an intricate web of evolutionary lines.
Finally, Homo sapiens emerged as the most innovative group, developing advanced tools, clothing, shelter, and outlasting all other Homo types. Despite our advancements, evolution is far from being done, and it will continue to alter us well into the future. As we continue to learn more about our evolutionary history, we gain a better understanding of our place in the world and how we have come to be the dominant species today.