Thursday, April 8, 2010
Our brain vs Evolution
Humans are the smartest creatures on this planet. With our brain being able to perceive everything that goes on in our day. It is the largest for our size and most complex. We say that we are descendent's from a common ancestor to chimps, but if our brain evolved shouldn't we see the chimps being pretty intelligent as well? The brain should have evolved over time, so that means that certain processes should be present in the chimps, but they are not able to do many of the things that our brain is physically capable of. How is it possible that our brain could have appeared from nothing?
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The flaw in your claim that the human brain “appeared from nothing” is that the only metaphorical leap our brains really had to make over the course of evolution was to become more advanced than the modern day Chimpanzee’s. The central nervous system of all primates is very advanced when relatively compared to the majority of other species that inhabit the planet and the human brain is not incredibly more complex than those of our primate friends. In fact, the difference between the genes that primarily determine brain size and complexity in chimps and in humans only have been shown to affect the cerebral cortex network, (in other words how the cells in the brain interact) not the cells themselves. Because of this we can basically say that our brains are made up of the same stuff as any other primates but we just have a lot more of it and it runs more efficiently.
ReplyDeleteNow as to why chimpanzees have not developed as much as we have since our divergent evolutions is somewhat tougher to answer. While we do not know everything about our common ancestor, it was probably very chimp-like but had the potential for an enlarged brain which is what lead to our complex, huge brains. We also knows that once a species comes into its niche and is perfectly able to survive and reproduce with very high likelihood then the process of natural selection and evolution will begin to slow down. We can speculate that chimps (like our common ancestor) fit their niche well and there was not a lot that mutations could do to vastly improve their fitness. On the other hand, the branch that was destined to stand up on two feet and would later form humans may not have fit its niche well. The larger skull size might have led to very advantageous mutations where an enlarged brain would be a result and would increase fitness. If this was the case then our brains (and our skulls as well) would have grown in size and complexity until the point we are at now. Our bodies have adapted to the increased energy demands that a larger brain requires and it has obviously worked out well for us based alone on our dominance of all habitats on the planet.
Sources:
http://news.softpedia.com/news/Genes-function-differently-in-human-and-chimp-brain-40039.shtml
http://www.medicalnewstoday.com/articles/4945.php
On the contrary, I would like to propose that chimpanzees and the like are quite smart. For example, in 2007, a study showed that chimpanzees were able to outperform even humans in a cognitive task. This cognitive task included remembering the locations of flashing numbers on a screen. "Adult chimps were able to remember the location of the numbers in the correct order with the same or worse ability as the humans, the three [out of three] adolescent chimps outperformed the humans...The youngsters easily remembered the locations, even at the shortest duration, which does not leave enough time for the eye to move and scan the screen." (Hooper)The Scientist that performed the experiment, Matsuzawa, has also been quoted: "We are 98.77% chimpanzee. We are their evolutionary neighbours."
ReplyDeleteChimpanzees, along with a few other primates, have also been known to pass the mirror test, where they recognize their own reflections. They are also known to learn from other animal's actions. When needed to cooperate to achieve a goal, this primate is no lone wolf. (Wiki)
Though the Chimpanzee have been at the top of the IQ chain for a while, recently, studies have shown a new primate to be the king. Orangutans. They have now been named as the world’s most intelligent animal in a study that places them above chimpanzees and gorillas, the species traditionally considered closest to humans. While studying orangutans a scientist found them capable of tasks well beyond chimpanzees’ abilities. These acticities include using leaves to make rain hats and leakproof roofs over their sleeping nests. He also found that in some food-rich areas the creatures had developed a complex culture in which adults would teach youngsters how to make tools and find food. The scientists suggest that the key factor in such developments is the orangutans’ life-style, spent mostly in the tops of trees where there is little risk from predators. This has allowed them to establish long and settled lives similar to humans’ and also to develop culture and intelligence.
However, Andrew, you were correct about one thing. The scientists studying orangutans also found that the single most important factor in deciding a species’ intelligence was simply the size of its brain: “The correlation of brain size with mental ability found in humans appears to extend throughout the primate order.” (Leake)
Sources:
Wiki: http://wiki.answers.com/Q/How_intelligent_are_chimpanzees
Hooper:
http://www.newscientist.com/article/dn12993-chimps-outperform-humans-at-memory-task.html
Leake:
http://www.timesonline.co.uk/tol/news/uk/article1654998.ece
Bio Book
I recently viewed an episode of Nova entitled: Becoming Human. It explained many theories behind how we became so intelligent. One thing that many scientists agree on is that "Every time there are these bursts of wild climate variability, human evolution takes a big step forward" (Townsley). He goes on to say during this interview that while other animals "fall back on the one thing they are good at" during this times of changing environment, "it seems that the response in our line of evolution was to grow bigger brains, which gave us the capacity to adapt to these swings." It wasn't the type of environment that paved the way for our huge brain growth, but rather, its dynamic quality that made being adaptable within a single lifetime, or smart, such an advantage. One key piece of this puzzle is that "In our resting stage our brain consumes 25 percent of our body's energy, and it is very difficult to, sort of, fuel the energy budget that this brain has without eating meat." Coming from a tree-dwelling primate, this was a large step away from the other primates, but obviously our species gained the ability to eat meat, making us omnivores. This gave us the energy budget needed to operate such complex pieces of hardware. The actual mutation that spurred our intelligence, according to Nova, was a very simple one. Apparently, there was a tiny nucleotide mutation in our genome that turned off the development of such large jaw muscles. Other apes have up to 200X the chewing power that we do, but this is because they have enormous chewing muscles that are anchored on the top of their skull. With these tight muscles gone, our skulls were allowed to grow larger without this hindrance, and the brain followed suit. And who ever said that monkeys were so dumb? They can do some pretty amazing things.
ReplyDeleteSources:
http://www.scientificamerican.com/podcast/episode.cfm?id=human-evolution-ii-recent-evolution-09-11-03
The complicated process of evolution explains why we are so much more sophisticated than other animals and that our brain did not appear from nothing. When animals have a common ancestor it means that they may share a few traits, but it does not mean that they have to be very similar, depending on how far back the common ancestor is in evolutionary history. The evolution of chimps and humans most likely occurred through speciation and one species split into two. When they separated, the evolution of each individual species was completely dependent on natural selection. Also it depends on whether or not either species had mutations that benefitted them. These mutations are completely random and very unlikely that two species would have a similar mutation, and whether or not they were chosen to survive and reproduce by natural selection. The environment is another determinant. Humans may have needed to adapt and develop quicker than apes because it may have been necessary to be able to live in their environment. Species evolve at a very slow pace (in the eyes of an individual), but many species evolve much faster than others, so apes may be more similar to the common ancestor than humans. The human brain is very evolved, while the brain of an ape is not quite as sophisticated. This is due to natural selection, the pace each species evolved, their environment, and mutations. These made it very possible for the human brain to come so far, while at the same time hindering the progress in the brain of an ape. “in the ape lineage, the brain has been expanding but along the human lineage it has really taken off” (plos). About four million years after humans diverged from great apes the human brain tripled in size, again showing that our brain has just grown and matured at a faster rate. Another reason we are so much more advanced than apes is because our cerebral cortex has grown very fast comparatively to other parts of the brain. The cerebral cortex has a key role in memory, attention, perceptual awareness, thought, language, and consciousness. This is a very strong reason that we are “able to perceive everything that goes on in our day” as stated in the post. It is the thinking part of our brain which resulted in us being more complex and complicated than many other animals. Evolution is a complicated process, and anything can happen.
ReplyDeleteSources:
http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030050
http://faculty.washington.edu/chudler/functional.html