Before we start, let’s look at three common misconceptions about human evolution. The first is that humans evolved from apes, gorillas, or chimpanzees. While we do share a lot of DNA with them, they are actually more like our evolutionary cousins. We share a common ancestor, but split from their evolutionary path about six to seven million years ago. Then, over the next several million years, our ancestors gradually evolved to early modern humans about 200,000 years ago.
Secondly, according to most theories, Homo sapiens just didn’t appear by themselves as the only species of human. Many scientists believe that there were at least 15 to 20 different types of early humans, which are part of the Hominin classification. These other groups of humans are called tribes. A notable one is Neanderthals. All other tribes of Hominin have died out except for Homo sapiens.
Finally, to say we are more evolved than our primate cousins is a bit misleading. Yes, we have a higher intelligence level. But if you and a chimp were dropped in the middle of the jungle, who would be more likely to survive? Instead, humans are the way they are because of the concept known as “survival of the fittest.” Essentially this means that we had the right tool, at the right time, and this ensured our survival. For example, let’s say you’re locked in an airless glass case with one random tool. If you have a saw, you may not survive, but if you have a hammer, you would. Being locked in that case with a hammer doesn’t make you better or more evolved. You just had the right tool at the right time. Evolution works in a similar way.
So now that we got that out of the way, the question becomes: what caused humans to evolve the way they did? One interesting thing to note is that since humans are so complex, and evolution took place over several million years, all, some, or none of these theories may be true.
10. The Stoned Ape Theory
Easily, the most far-out explanation for why humans evolved is that they ate psilocybin mushrooms; also known as magic mushrooms. The theory comes from Terence McKenna. As you may have guessed, he was a strong advocate for recreational use of psychedelic drugs made from plants.
McKenna’s “Stoned Ape Theory” is that, about 18,000 years ago, near the end of the last glacial period, the jungles of North Africa started to recede and gave way to the grasslands. Our ancient ancestors came down out of the trees and started to follow around a herd of ungulates, which are large mammals like horses and rhinoceroses. Our ancestors ate the magic mushrooms that started to grow in their dung. McKenna also claims that the mushroom spores came from outer space. Supposedly, our ancestors mostly lived off the mushrooms, which altered their minds. This led to the development of spoken language.
However, 12,000 years ago, due to climate change, the mushrooms were largely removed from their diet. While their brain had evolved so they could talk, early humans ultimately reverted back to their primate social structures, ones that we are still living in today.
Of course, not many people in the scientific community think the theory is true. But there is evidence to back it up. For one, mushrooms are pretty resilient because they can grow in the dark on decaying organic material, so there’s a good chance they could survive on alien planets. Also, spores can be moved by electrostatic forces, which are rather weak, so they travel well. Finally, scientists have recently shown that magic mushrooms do change brain connectivity. So, just maybe, McKenna was on to something. But more likely, he was just on something.
9. The Aquatic Ape Theory
One thing that separates us from a lot of other tribes of Hominin, and other mammals in general, is that we are nearly furless. Researchers aren’t exactly sure why we lost most of our body hair, but it’s believed to be for evolutionary reasons. One theory that was first proposed in the early 1940s is “The Aquatic Ape Theory.”
The theory is that 6-8 million years ago, our apelike ancestors looked for food by swimming. However, fur isn’t ideal for life in the water. So, we shed the hair and developed higher body fat, like aquatic mammals such as walruses and cetaceans (whales and dolphins). The theory is controversial and has yet to be proved.
8. One Human Started it All
In the introduction, we talked about how evolution happened over millions of years. It was a bunch of small changes, and not one sudden, drastic change. A theory that goes completely against this comes from Colin Blakemore, an Oxford neurobiologist. His theory is based on the fact that, about 200,000 years ago, there was a huge jump in the size of the human brain, where it increased about 30%. This sudden increase was odd because, starting three million years ago, the size of the human brain only gradually increased.
Blakemore believes that this jump was caused by one person, a woman who lived about 200,000 years ago that all humans can be traced back to called “Mitochondrial Eve
.” He speculates that she had a mutation in her brain, that either first happened in her
brain or was passed on to her by a close relative. This mutation led to massive brain growth. Blakemore says that even a change in one gene would have been enough for the brain to grow as big as it did. Also, the genetic mutation was so dominant that it was passed on through generations. Then, when environmental conditions changed because of things like climate change, droughts, and other problems, the descendants of Eve would have been more capable of handling the problems, making them better able to survive.
7. The Killer Ape Theory
Violence is considered one of the worst human traits, but it may be the reason for our evolution. According to “The Killer Ape Theory,” which was first proposed by anthropologist Raymond Dart in 1963, the fact that humans are aggressive, like violence, are cruel, and will kill in cold blood are the reason that humans evolved. The theory says that early humans would move into other areas, even ones they didn’t need, and through vicious acts, which included cannibalism and killing members of other tribes by ripping them limb from limb, they would take over the area.
This would have a three prong effect. First is that it would decrease the population of other tribes of Hominin. Second, our ancestors would have had the best areas of land and access to the most resources. Finally, if they moved into an area and killed all the males, then they would have mated with the women, ensuring that human DNA was passed on. However, evidence to back up the theory is inconclusive.
Another theory as to why our ancestors shed their fur was to rid themselves of parasites like ticks and lice. These parasites would not have only been annoying, but would have carried diseases with them like malaria, West Nile, and Lyme disease. In some cases, these diseases would have been deadly.
The problem was fur is needed on most primates because it helps regulate body temperature. This is where the human brain comes in. Humans could do two things that other Hominin couldn’t: build fires, and make clothing. This would have helped us regulate our body temperature, thereby eliminating the need for fur.
A major difference between Homo sapiens and other species of Hominin is that we were able to build fires. In turn, this allowed us to cook our food. According to researchers, cooking two types of food helped in our evolution. The first one is meat. Human ancestors started eating meat about 2.6 million years ago, but it’s possible they were butchering meat as early as 3.4 million years ago. Eating meat had a twofold effect on human evolution. The first was that the diet would have altered the brain by creating more neurons. Secondly, hunting for food was a group activity that would have helped early humans develop verbal communication and planning skills.
The other food that helped in our evolution, which may surprise devotees of the Paleo diet, is carbohydrates. A study from the University of Sydney found that the human brain would not have been able to evolve unless early humans ate meat and starchy carbs like nuts, fruits, and vegetables similar to potatoes. The carbs were needed for the evolution of the brain because the human brain needs glucose in order to function. In fact, the brain uses 60% of the blood glucose, meaning early humans would have needed carbs in their diet.
4. Climate Change
Since the days when early humans first appeared, the Earth has undergone hot spells and cold spells. Each time there was a major change in climate, it coincided with large evolutionary leaps
, like bigger brains and the ability to use complex tools. This has led researchers to believe that humans evolved to deal with the uncertainty of the environment.
The problem with the theory is that researchers aren’t sure why climate change would have caused these giant leaps. However, they believe that every change could have impacted a different trait. For example, when the earth was hot and there was less water, early humans would have needed to learn to plan to ensure they get water and food. But then during wet periods, planning wouldn’t have been as necessary and something like sexual selection could become more important.
All of these traits that were affected by changes in climate make up the mosaic of the modern human.
About 60,000 years ago, early Homo sapiens left Africa. When they did, they encountered other Hominin like the Neanderthals and the Denisovans and all of us got a little busy with each other. This intermingling led to a hybridization
, which altered the human evolutionary line. This interbreeding would have sped up changes in evolution. These changes would have helped us adapt in areas outside of Africa, which allowed humans to spread across the planet in about 45,000 to 55,000 years.
Evidence to back this up is that people today have traces of Neanderthal and Denisovan in their DNA. Genetic testing shows that Europeans and Asians have about one to four percent Neanderthal DNA and people from Southeast Asia have up to 6% Denisovan DNA. As for people who never left Africa, about 3,000 years ago, there was a migration back to Africa. So even African people have some traces of Neanderthal DNA.
2. Walking Upright (Bipedalism)
One of the major things that set humans apart from our Hominin relatives is the size of our brain. Over the course of human evolution, the human brain has more than tripled in size and the cerebral cortex, which is responsible for complex mental functions, was reorganized. This change happened about 200,000 years ago and researchers are unsure why.
One theory is that it may be a result of humans walking on two feet, which started about four million years ago in one of our ancient evolutionary ancestors. The theory is that over this time, the shape of the pelvis changed and the birth canal became narrower. This led to babies being born with soft skulls so they could maneuver through the narrow birth canal. Due to the soft skulls, it allowed the human brain to expand, thus leading to modern day humans millions of years later.
1. We Could Throw Things
Located in the Republic of Georgia is Dmanisi
, the oldest known Hominin
settlement outside of Africa. The fossils from the area are about 1.8 million years old and Dmanisi may hold a clue as to why humans evolved. Based on findings at the site, researchers believe that humans evolved because our ancestors could throw rocks.
The theory is based on the fact that our ancestor, Homo erectus, survived in the Dmanisi area despite the presence of large cats, like saber-toothed tigers and leopards. The Dmanisi people were small and didn’t have much in the way of natural defenses, like claws or fangs. At the site, the researchers found plenty of rocks, which led them to believe that, at first, early humans used rocks by throwing them at large predators to keep them away while they ate. Eventually, the ability to throw rocks was used to hunt and to trick the big cats and steal their food.
This ability to throw made us more human in two different ways. One is that it helped socialize us because bands of humans would have worked together to hunt and trick other predators. Secondly, in the brain, there’s something called Broca’s area. This is a region of the brain that’s responsible for hand and eye coordination, which is needed to throw a rock at a target. The region is associated with higher mental functions such as speech and communication. That means there’s a chance that throwing helped developed speech, which was a major milestone in the evolution of humans.
Human Evolution Handbook