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Why Are Human Brains So Big?

livescience.com — Compared to almost all other animals, human brains are larger as a percentage of body weight. And since the emergence of the first species in our ***** genus (***** habilis) about 2 million years ago, the human brain has doubled in size. And when compared to earlier ancestors, such as australopithecines that lived 4 million to 2 million years ago.

Who dugg this? Made popular Jul 13, 2009

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  • mostie, on 07/13/2009, -0/+45To make the hunt worthwhile for zombies
  • radicaldementia, on 07/13/2009, -4/+33One problem I see with these hypotheses is they strongly correlate brain size to "processing power", however I do not believe that getting a larger brain necessarily corresponds to increase in intelligence. For example:

    1 - elephants are one animal that have larger brains than humans. They certainly have shown a decent intellect, but they are still overshadowed in every respect by humans.

    2 - Jumping spiders, which are often a half-inch or smaller and have literally have a pinhead brain, seem to possess visual processing capabilities on par with many higher animals.

    3 - We know that people with conditions such as Down's syndrome have normal-sized brains, but clearly they are wired differently and result in a severely impaired intellect.

    4 - There have been cases of people who have had hemispherectomies (removal of half the brain) who have led fairly normal lives afterwards with only minor impairments. One person went though college and was considered to be highly intelligent.

    I think we can assume that there is a weak correlation, that there has to be some minimum size to possess a certain level of intelligence. The real unanswered question though, is what is this minimum for various degrees of intelligence and how close was our brain-size to this minimum as our intelligence evolved. An increase in human brain size would mean nothing if we can demonstrate that we could posses the exact same intelligence with the smaller brain of our ancestors. Instead, it would be the way the brain wired itself that was of significant importance, with an increase in size being a side-effect.
  • borez, on 07/13/2009, -5/+28Bacon stimulation.
  • gdo01, on 07/13/2009, -0/+20Ape penis is especially small...so small. Ape cannot achieve much with so small penis. But you, humans. Wow, penis so big, so big penis.
  • Hetman, on 07/13/2009, -0/+18I was always under the assumption that it was a brain size to body weight ratio. As you mentioned a jumping spider has a small brain for a jumpin spider but how does it compare to the size of its body.
  • the2989, on 07/13/2009, -0/+17This is what the discription looked like before I signed in.

    Compared to almost all other animals, human brains are larger as a percentage of body weight. And since the emergence of the first species in our ***** genus (***** habilis) about 2 million years ago, the human brain has doubled in size. And when compared to earlier ancestors, such as australopithecines that lived 4 million to 2 million years ago. More…

    lol digg, since when is "*****" a word offensive enough to censor?
  • CrankMyBlueSax, on 07/13/2009, -3/+15Giant brains allow us to spend more time fantasizing about sex, thus leading to internet porn and living in Mom and Dad's basement.
  • Parastie, on 07/13/2009, -0/+11If you actually read the original paper (not this report, though it mentions it) they're trying answer why human brains increased in size, not so much proving that larger size = more intelligence. It's been proven that increased connections is what makes us more intelligent, however increased sizes allowed for larger folding in the brain and more connections.
  • lordmike, on 07/13/2009, -1/+12My one friend who's a biologist has told me that the gestation time for humans SHOULD be almost 2 years in the womb (like elephants)... which is why infants are so incredibly helpless when they are born, 'cos they are born too young. The reason why we have to give birth at 9 months is that our skulls would be too big to exit the birth canal if we the baby waited any longer to get out... That's also why human childbirth is so incredibly difficult compared to most other animals--our heads are simply too big!
  • Tanktunker, on 07/13/2009, -1/+11What's that you say?
    I have an enormous penis?
  • Hetman, on 07/13/2009, -0/+9Will evolution is kind of like gravity. You may not see it but it is happening all the time. If you really do believe the moon landing where faked and you are not being a trool, Japan plans to be the next person to land someone on the moon. If they do will you still beleive it is a conspiracy?
  • Frankyfan3, on 07/13/2009, -0/+8Actually, you are onto something... our ability to process and cook food seems to have played a roll in our ability to focus energy on large brain development.
  • inactive, on 07/13/2009, -2/+10"We" is a plural pronoun. You're looking for the singular "I".
  • Disgod, on 07/13/2009, -0/+8"really.. all this complexity (still way beyond human understanding) from nothing but the laws of physics and chemistry?"

    Really... all that complexity in a god FROM NOTHING!!! Not even laws of physics and chemistry. Look up the logically fallacy "special pleading". You're asking the question about the Universe, but you're not asking the same question of something which would, by necessity, be infinitely more complex than the Universe itself.

    "why would the unbiased laws of chemistry and physics favor order over chaos? "

    Study a bit of both and you'll understand. With physics, simple gravity brings mass together, which becomes more ordered, which leads to the development of stars, and all the elements that they produce. Then those elements react to each other in known ways, and so on leading to planets where chemicals interact for hundreds of millions of years growing in complexity just from interacting with each other. There are lot of questions about specifics, but the overarching picture shows that order can arise from chaos based on a few fundamental forces. The origins of life are becoming understood. Scientists have discovered how ribosomes, nucleic acids, RNA, amino acids, proteins, and primitive cell walls can develop under completely natural conditions which are the result of early physics and chemistry.

    "come on..the emperor has no clothes.."

    Only if you have zero understanding of science, chemistry, biology, or physics.
  • diggduggDOOM, on 07/13/2009, -0/+8Check out the big brain on Brad.
  • trendygamer, on 07/13/2009, -1/+8Because our primary evolutionary mutation is our intelligence, and that's the organ that controls it.

    We sent a goddamned man to the moon.
  • CrazedLeper, on 07/13/2009, -3/+9"Just knowing we're in the same genus makes me ashamed to call myself '*****'!"

    ---Professor Farnsworth.
  • ApokalypseNow, on 07/13/2009, -0/+6"why would the unbiased laws of chemistry and physics favor order over chaos?"
    Because the earth is not a closed system, because entropy in a thermodynamics context means "the unavailability of a system's energy to do work", and because of Ilya Prigogine's 1977 Nobel Prize work on thermodynamics and dissipative structures, as well as Jeffrey Wicken's 1979 work on the thermodynamical explanation for the evolution of complexity, and how it is expected because complexity-generating processes dissipate the entropy (NOT CHAOS OR DISORDER) from solar energy influxes, in accordance with the 2nd Law of Thermodynamics.

    Your ignorance of the facts does not constitute a rebuttal of them.
  • lyonsban, on 07/13/2009, -0/+6@radicaldementia
    A certain amount of the brain is used to control the body. Encephalization quotient is another name for it. The larger the body, the larger the minimum brain size needed to control it. The size of the body is important too though, as small animals like rodents have a higher EQ than a whale does, even though the whale may be more intelligent. Think of it as a rough rule of thumb for determining brainyness.

    That is why brain mass/body mass is important. Otherwise elephants would be hunting humans for their shiny teeth rather than the other way around.

  • damnshoes, on 07/13/2009, -0/+5I think you're onto something!
  • ApokalypseNow, on 07/14/2009, -0/+5There's nothing religious about an observable process and an evidence-based hypothesis. Your continued denial of objective reality has no effect on how it works.
  • kingmanic, on 07/13/2009, -0/+5I heard a archaeologists say that the origin of cooked food may also have helped as it reduces chewing time allowing more time for other activities as well as providing more variety in what can be eaten and for how long harvested food can be stored.
  • inactive, on 07/13/2009, -3/+8The Texas board of edumacation is addressing the problem of large brains in humans as we speak.
  • kalvinb, on 07/13/2009, -0/+5Unlike animals, humans aren't perpetually living in the moment. Humans are able to retain a significant amount of information. Animals remember very little since they mostly operate on instinct.

    The larger brain and brain density is largely for remembering 80+ years of life.

    http://news.bbc.co.uk/2/hi/science/nature/677048.s ...
    "Cab drivers' grey matter enlarges and adapts to help them store a detailed mental map of the city, according to research. "

    Apparently the scientists in the Live Science report missed that study.

    With increased access to storing and retrieving information electronically, brain size may become stagnent. You no longer need to keep 80+ years of life in your head. You write it down and take lots of pictures. Taxi drivers no longer need to remember all the roads. They just use GPS.
  • Sieker, on 07/13/2009, -1/+5You'll find that as the brain grows larger proportionally to the body, the prefontal cortex grows as a greater proportion of the whole brain. The prefontal cortex:

    "...has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior. The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals." (http://en.wikipedia.org/wiki/Prefrontal_cortex)

    If I had to define intelligence in an evolutionary sense, that wouldn't be the worst place to start.
  • PowderedToasty, on 07/13/2009, -0/+4Read a book or two while you're hiding under your umbrella. It's actually really interesting.
  • Mnementh2230, on 07/14/2009, -0/+4"that's why there haven't been any *lately*."

    There hasn't been any reason to go to the moon *lately*. It is VERY expensive, and there's no real benefit to it except national pride at this point. Why go when you're not getting anything tangible out of it?

    You've yet to answer this question.
  • inactive, on 07/13/2009, -2/+5Oh Great now I have an obese brain!
  • praisethelard, on 07/13/2009, -1/+4I believe intelligence has more to do with brain density.

    Here's an interesting study: http://www.jneurosci.org/cgi/content/full/26/40/10 ...
  • kingmanic, on 07/13/2009, -0/+3We also have one of the longest sex acts. Most other mammals are done within seconds. We stretch it out for minutes to hours.
  • Sieker, on 07/13/2009, -0/+3That probably started when proto-human females started masking their fertility cycles (no "heat" or "mating season" for our kind). Sex without direct procreative purposes = sex for fun and for pair bonding.

    In other words, don't tell me size doesn't matter. It's been evolutionary selected since we started ***** for the ***** of it.
  • fury420, on 07/13/2009, -0/+3I dunno, it could prove rather useful in a natural disaster, environmental calamity, etc... Plus, long distance travel does have its uses, especially for food collection. travel from a base camp in a fertile river delta to far off oceanfront locations for fishing, crabbing, harvesting of other sea crops, etc... for example could prove very useful, as shown by many semi-nomadic native tribes who travel vast distances to a winter or summer living area.
  • drmangrum, on 07/13/2009, -0/+3If by hours you mean resting and going at it again later, ok.

    If by hours you mean the same session for hours, I have to doubt that. Just the idea of keeping it up that long seems....annoying.
  • kingmanic, on 07/13/2009, -0/+3drmangrum: Some people suffer from several conditions which make this not only possible but likely. Look up 'retarded ejaculation'. Although more than one hour is unlikely unless you have a very very patient partner; you can hit an hour of continuous sex easily.
  • tedpark, on 07/13/2009, -0/+3Don't you get a t shirt and a medal?
  • Mujokan, on 07/13/2009, -1/+3http://en.wikipedia.org/wiki/Dunbar's_number

    "Primatologists have noted that, due to their highly social nature, non-human primates have to maintain personal contact with the other members of their social group, usually through grooming. Such social groups function as protective cliques within the physical groups in which the primates live. The number of social group members a primate can track appears to be limited by the volume of the neocortex region of their brain. This suggests that there is a species-specific index of the social group size, computable from the species' mean neocortex volume"
  • IKORKYI, on 07/13/2009, -1/+3My Mama says the earth is 6,000 years old and that alligators are ornery because they got all them teeth and no toothbrush.

  • novenator, on 07/13/2009, -2/+4That's not all that's big. ***** Sapiens have enormous penises compared to the other Great Apes: http://www.associatedcontent.com/article/42665/pen ...
  • cfuse, on 07/14/2009, -0/+2Digg is in America, the land where you can be sued to death for minor butthurt and it's so prudish that Janet Jackson caused a titpocalypse.
  • chongli, on 07/13/2009, -0/+2Do elephants have complex oral traditions and mythologies? Do elephants even have a language?

    Many other mammals and even non-mammals such as reef squid have some of the "cultural" aspects you described, they do not have culture.
  • Mujokan, on 07/13/2009, -0/+2It's not ratio to body size that matters, but what you are processing. You can get good visual recognition out of a neural network with very few elements, and evolution has had a butt load of time to refine it.

    Anything non-linear where you have to estimate and predict the outcomes of the interactions of a bunch of different variables takes a lot more processing than judging how far to jump. Then when you get self-reference into it (what do they think I think they think) you have another jump. Translate it all into abstracted, logical language form and then you need human-size brains.

    You can get the processing power of an insect on a desktop. Artificial intelligence at a human level is still far out of reach.

    Of course it's not just size that matters, but organization. What do elephants have to talk about? It's not like they have much in the way of culture. Humans start out with loads more neural connections than they finish with. In childhood the connections are winnowed as kids learn to think consciously. This is something we've evolved towards.
  • naldwell, on 07/13/2009, -0/+2I agree, I think LSD is an evolutionary force that shaped the baby boomers worldview and now seems to be back in force (if it ever went away?) judging from the hundreds of 20-something LSD users in my city at least. I just love the way they look at me with those 'yes, we know' eyes.
  • Sieker, on 07/13/2009, -0/+2Yeah, the crow studies showing them using second-level logic to solve puzzles for food makes me uncomfortable.

    Watching a chimpanzee play with colored blocks for food makes me smile.

    http://www.youtube.com/watch?v=dbwRHIuXqMU

    that scares me.
  • novenator, on 07/13/2009, -0/+2Exactly.
  • lejaffe, on 07/13/2009, -2/+4I can't believe that DIGG can't handle the word "H_0_M_0", even as a prefix.
    For Shame@
  • AtomicTheory, on 07/13/2009, -1/+3The phrase from the description "And when compared to earlier ancestors, such as australopithecines that lived 4 million to 2 million years ago" is not a complete sentence.

    BURIED!
  • RudeTurnip, on 07/13/2009, -0/+2When I die, you're going to get a lesson on the law of averages.
  • fredcondo, on 07/13/2009, -1/+2The obesity epidemic is nature's way of correcting our brain:body mass ratio.
  • Enterres, on 07/13/2009, -1/+2The reason why our brains are so unique and interesting in so many ways is because for countless generations our ancestors were tripping out on DMT probably on a daily basis. DMT is one of the most powerful hallucinogenics, and is the drug which is thought to herald the beginnings of consciousness when we are during the first few weeks in the womb.
    This is the only reasonable explanation for why our minds are so...weird. The very nature of humanity is contrariness, and making any given thing more complicated than it has to be. There are numerous mysteries regarding the stupid meaningless things we do like sneezing, orgasms, thinking & feeling, and other social functions - because the fact of the matter is that our evolutionary vehicle is, was, and probably always will be mind ***** drugs.
    Go read Wolf's Electric Acid Kool-Aid Test and tell me that some stupid scientist in a lab coat somewhere, or that Michael Phelps is really the driving force behind our latest evolution - not likely. It's all about the drugs, peeps.
  • brian1625, on 07/13/2009, -2/+3Ah, so this is why I've added you as a friend a while back.

    I would say that under normal circumstances humans genetically have larger brains than any other primate brain size appears to matter. The correlation is clear, social size of primate groups correlates with bran size as well as intelligence. If the comparison is being made amoung primates brain size is an adaquet question to ask. Why are Human Brains so big? and Is it a necessity or merely side-effect of the way our brains evolved?

    Though I agree, among animals in general the size to intelligence ratio is not as significant as people seem to think. Another example to add to your list is the new discoveries in bird brains. So I agree, they're asking an interesting question, but it's not that significant.
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