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5 Surprising Facts about Human Evolution
1. It's all in the Hips
Most people tend to think the first thing to evolve, or even the most pivotal, were our large brains. This isn't true! It's actually what we teach toddlers to do: walking, or bipedalism. It was one of the first traits we evolved as hominids. Fossil records all over Africa confirm that bipedalism was one of the first major adaptations we made as a species. This isn't to downplay our brains, it's certainly a major adaptation, but brain size didn't actually increase until (in evolutionary terms) fairly recently.
Walking, running, and standing upright is made possible by our skeletal structure. Our hips must be perfectly aligned with our spinal column to correctly balance our weight, and still bare the load of the upper body. Our legs must align properly with the shifting weight of moving forward, and our heel and toes must bare the load. Our knees must lock to make the entire thing even worth the amount of calories it takes go through the effort. Chimps and Apes, for example, expend 60% to 70% more calories when they "walk" going the same distance as a human simply because their knees don't lock. All these structural changes occurred in an astonishingly short period of time, meaning there had to be some massive pressure driving evolution. Around the same time our species developed these traits in Africa, the continent was drying out -- plains and savanna appeared where forests had been.
The advantages, given these climatic changes were an ancient hominid could have moved through the tall grasses of the dry regions and still see predators. It also made our ancestors seem larger than they actually were, which could have made predators think twice. Probably the best thing: it freed our arms and hands to create tools, collect food, and use weapons.
2. Agent Smith may have been right
If you've seen The Matrix, you may remember the line by Agent Smith when he said, "Humans are a virus...". I know I objected, but, he may have been right. At least in this sense:
Deep in our DNA there are genes we didn't inherit from our hominid ancestors. We didn't even get these genes from mammalian ancestors, or reptiles, or any identifiable ancestor. These genes are actually viral. In fact, they're retroviruses. They reproduce by "hijacking" a cell, and using the cell's own machinery to make more viruses. Sometime in the past, viruses hijacked the cells of our ancestors, most likely an ancient mammalian creature, and infected their gonads (yes, that's an actual scientific term). Their offspring carried this genetic information with them. Most of it is actually "junk DNA", which doesn't really code for anything (but does actually act as a layer of protection for the DNA that does). Some of it is actually pretty vital to reproduction, however, and in mammals it codes for several structures of the placenta.
3. Look Who's Talking
Language has for ages been considered by scientists to be the distinguishing factor of our species. It's not just that we need it to transmit culture from one generation to the next, to teach, and some posit, even to think -- it's was long considered that only we had it. Of all the living primates today, we certainly are the only ones that possess a true recursive-grammatical system, which means we can speak words in infinite combinations and still have them make sense. Research is still in progress on some species, like dolphins, and whales so I can't comment with much validity on their "language". I know there's the famous example of Coco the ape that knew sign-language; but apes don't naturally sign to one another in the wild (and their audible grunts are signals and warnings, not true language), so as far as Anthropology is concerned, that doesn't count.
But there was one species that does give a clue that it may have possessed true language. Neanderthals. Although their name is synonymous with stupidity today, they were actually quite intelligent. Their brains were on average 200 cc. larger than the average human's brain at the time. They created tools, hunted with great efficiency, and even buried their dead. All signs of a complex culture. Given these factors, it seems they were certainly mentally capable of language. More recent excavations have uncovered that they were also physically capable of it as well. They possess a hyoid bone, in fact, it's identical to the hyoid bone in humans. The hyoid makes speech and vocalizations (or anything more than a growl or grunt) possible.
What their language may have sounded like is impossible to know. However some have hypothesized that the very first archaic languages of humans had clicking sounds, similar to the clicks heard in some African languages today, and that these modern languages may have actually just retained these sounds. As humans moved out of Africa and encountered (and inter-mated with) Neanderthals their languages' phonetic systems would have changed accordingly. Meaning, Neanderthals may have had a phonetically melodic system. Again, though, that's all conjecture; but it's fun to wonder.
4. Endangered Species
We humans almost went extinct. In fact, genetic studies indicate that our population went low enough that we would have been eligible to be on the Endangered Species List -- with only around 3000 humans left on the face of the earth, down from an estimated 2 million.
How did this happen? The most likely explanation is an environmental catastrophe. Our population was laid low between 70,000 and 60,000 years ago. Geological records indicate that around the same time ash was in the atmosphere, creating winters where they shouldn't exist and upsetting the climate. An eruption of a super-volcano could have done this, especially if combined with a harsh ice-age period. The result was a so-called "genetic bottleneck". Where only some members with many of the same mutations of our species endured and survived. This may explain why in comparison to other primates, our genetic codes are actually fairly uniform. Chimps, our closest genetic cousins actually have far more variability in their genes on average.
A collection of interesting phenomenon began to occur during and after this period. Tool production and complexity increased markedly. The very first cave paintings, jewelry, and art began to appear. Inventive strategies of saving water, like storing it in shells, gourds, or skins began occurring. In other words, we began making giant leaps in technology. It's still debated whether this change was largely environmental pressures creating cultural changes, or mother nature making some genetic changes. In either case, the offspring of the survivors inherited these changes; and thrived.
5. It ain't over yet
Our evolution as a species isn't over. We are still evolving. Vestigial organs are usually cited as evidence, however, their size, and general lack of functionality have actually been fairly constant for at least the past 100,000 years, as indicated by extrapolations from the fossil record. Vestigial organs are, however, evidence of our earlier evolution from our hominid ancestors; such as the australopithecines, whose large jaws and appendix worked together by crunching down on large tubers and excreting digestive juices to extract energy. But there are two more recent ways in which we can observe our present state of evolution:
- Our brain sizes are actually decreasing. This may sound shocking, but over the past 30,000 years our brains have actually shrunk from approximately 1,500 cc (cubic centimeters), to 1,350 cc. This is equivalent to a tennis ball. Why are our brains shrinking? Well, bluntly put, we could be getting dumber. The more hopeful answer is our brains are actually getting more efficient, and simply don't need the extra mass to do the same amount of work. Similar to the way cell-phones seem to constantly shrink in size. What's the evolutionary pressure causing this? Well, considering our brains are energy hogs compared to every other organ, they use-up some 30% of our calories, even a small reduction in size would mean more calories to go around, and in times of starvation, every little bit counts.
- There are several groups of genes, approximately 2,000, which have only become prevalent in modern Humans over the past few thousand years, though starting upwards of 40,000 years ago. Many of these mutations are devoted to fighting disease. More than a dozen of these mutations are linked to Malaria in particular and even now are spreading throughout populations in Africa. Many more of these genes are linked to leprosy, tuberculosis, and even the bubonic plague. This may very well be natural selection selecting for city-dwellers, as cities have historically been centers of economy, culture, and disease. Of course, I'm not just talking about the densely populated cities of today, like Chicago or Paris; even a small town with a few hundred people would have been huge metropolis to our hunter-gather ancestors.