This term I’ve started teaching a new module ‘Cognitive Evolution’ with my colleague Dr Sam Smith. We’re only two weeks into the start of the term but already it’s throwing up some really interesting questions about why Homo sapiens have such large brains. Not just a little bit big, but really really big! If you compare the primates to all other mammals then they emerge as being ‘brainier’ but then when you look inside the primate order it’s the genus Homo that really start to look like an outlying group. When you look within the genus there are roughly four species that start to follow the pattern of having big brains and display ‘advanced’ behaviours (namely Homo ergaster, Homo heidelbergensis, Homo neanderthalensis and Homo sapiens). It can be so easy to see this as an inevitable pattern of bigger = better. Brains get bigger and technology becomes better etc. But the archaeology does not directly correlate with the fossil data – for instance Homo ergaster continued to use Mode 1 tools for about 400,000 years before developing Mode 2 Tools despite having a brain almost twice as large as Australopithecus (Homo) habilis the ‘first; stone tool maker.
Selective pressures are really hard to identify in the fossil record and it notoriously easy to create a misleading narrative (we humans do love a pattern) when looking at human evolutionary themes. In other words just because we have big brains and use them to do lots of whizzy things today that’s not the same thing as understanding why they evolved. That’s whats so frustrating – the reason our brains are so large is one of the key questions facing palaeoanthropologists but why they did evolve is so hard to fathom. The selective pressures must have been immense to have evolved such a large and energy consuming organ. Big brains need energy, ours consumes roughly 22% of our daily calorific needs – for natural selection to have produced this state the evolutionary need must have been huge since regular access to high calorie food resources would have been vital for survival. As ever with human evolution there are a number of competing theories – some argue that our brains have evolved to allow for ever increasing social complexity, while others point towards the relationship between brain size and technological complexity. I lean towards manipulation as one of the key drivers of selection for bigger and bigger brains in Homo. This ‘lying, cheating and stealing’ model might not be the most uplifting of thoughts but certainly fits with our behaviour as a species.
Tags: Cognition, Hominins, Human Evolution
thescienceofhumanevolution 
08/10/2012 at 04:01 |
The why our brain is so large is simpler than we care to admit, I don’t think it was about technology but of a supply and demand, the need for meat protein, as is my understanding that meat was the principal reason for us turning into the humans that we are homo sapient, for it was the method of the hunt that help enlarge the brain, the method not the meat, not having the technology of bow and arrows they had to run after fast animals into exhaustion before approaching for the kill, bottom line of the enlargement of the skull came from the thinning of the bones, to run faster H.S. needed to lose body mass and bone density, the muscles that holds the jaw attached to the skull also became weak allowing the skull to grow, with a bigger skull a bigger brain and that is us in a nut shell.
the Neanderthals had strong jaw muscles keeping their skull from growing tall, instead theirs grew long even though it’s brain may weigh the same it does not equate to been intellectually similar as that of homo sapient, I cannot tell you why the human brain evolve this way but I can guess that every component of our brain just grew , doubling in size until it stop growing influenced by the female pelvic bones and birth canal, this is what some scientist have suggested and I believe it to be true.
08/10/2012 at 23:58 |
Drs: thank you for tacking this interesting topic of human cognition, I hope you can figure it out.
I have a topic that may interest you, is about teeth size and the various gene contributors to each distinct size teeth, a study like this may shed some light on how many genes contributors are influencing our jaws, have you not questioned why some people have a gap on the upper jaw and some have two big upper front teeth, crooked teeth, perfectly straight teeth, small teeth, it’s just my opinion but I think this are influences from our past, as far back as they “our ancestors” have been evolving starting from apes, away from apes to us now. been how DNA is not going to help you figure out us from our ancestors may be you and your colleges can compare the physical evidence from one specimen to the next for a better understanding, teeth is just one of those things that can be compare even a small variation can make a big difference in our jaws as to how they fit, perhaps is the jaw itself that makes the differences, I have one question do you think teeth evolve genetically as easily as bones do or other parts of the body? as I am sure they do but It may endure time and cross breeding, for the evidence in us is obvious to me.
I have other comparison ideas that perhaps you may be interested in, ideas that may require a team of Drs like your selves for a thorough examination of particular ideas.