# are human brains getting bigger? **URL:** \ **Category:** Factual Questions\ **Created:** [October 28, 2004, 3:46pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681 "2004-10-28T15:46:27Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![drhess](https://avatars.discourse-cdn.com/v4/letter/d/94ad74/32.png) [@drhess](https://boards.straightdope.com/u/drhess)\ **Post date:** [October 28, 2004, 3:46pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/1 "2004-10-28T15:46:27Z")
As humans get bigger over the past many decades (not just fatter, but taller, etc.), are brains getting noticably bigger, and if so, is it useable matter or just “empty space”? :dubious: ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 28, 2004, 4:11pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/2 "2004-10-28T16:11:14Z")
Just to address the real question, there is no known correlation between brain size and intellect in modern human populations. Yao Ming has a much bigger brain than Paul Hamm, but that doesn’t make Yao Ming any smarter. Our brain power probably comes as much from the internal wiring (number of connexctions between neurons) as anything else. If you could measure THAT, you might find a correlation between it and some aspects of intelligence. ---
**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\ **Post date:** [October 29, 2004, 1:53am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/3 "2004-10-29T01:53:58Z")
> [@John Mace](#): > > Our brain power probably comes as much from the internal wiring (number of connexctions between neurons) as anything else. If you could measure THAT, you might find a correlation between it and some aspects of intelligence. There are also several other factors that I found [here:](http://www.lrainc.com/swtaboo/stalkers/em_intmy.html) > [@](#): > > Many observations concerning intelligence could be explained if much variance in intelligence reflects myelination differences. More intelligent brains show faster nerve conduction, less glucose utilization in positron emission tomography, faster reaction times, faster inspection times, faster speeds in general, greater circumference and volume, smaller standard deviation in reaction times, greater variability in EEG measures, shorter white matter T2 relaxation times, and higher gray-white matter contrast with magnetic resonance imaging. Also explainable are peculiarities of the increased reaction times and standard deviations with number of choices and complexity, reaction time skewness, the shorter latencies in evoked potentials, shorter latencies to the P300 wave, the high glial to neuron ratio in Einstein’s brain, less glucose utilization per unit volume in large brains, certain results related to lipids, essential fatty acids, and cholesterol in adults and premature babies, and the survival of genes for lower intelligence. Children’s improved performance with maturation might result from myelination. The slowing of response times with age, the decline in intelligence, and increased T1 relaxation times could be explained. Differential myelination in the mouse brain might be able to explain the heterosis observed for myelination, brain size, caudal nerve conduction velocity, and maze performance observed. ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [October 29, 2004, 4:14am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/4 "2004-10-29T04:14:55Z")
> [@drhess](#): > > As humans get bigger over the past many decades (not just fatter, but taller, etc.), are brains getting noticably bigger, and if so, is it useable matter or just “empty space”? :dubious: I’ve seen no stats either way, but it would be difficult for human brains to get significantly bigger. Babies’ heads barely fit through the birth canal as it is, which is why human births are so traumatic compared to other mammals’ births. Women’s pelvises would have to get wider, which in turn would mean they could hardly walk properly let alone run. So it’s hard to see that it’s possible. ---
**Author:** ![Loopydude](https://avatars.discourse-cdn.com/v4/letter/l/e56c9b/32.png) [@Loopydude](https://boards.straightdope.com/u/Loopydude)\ **Post date:** [October 29, 2004, 4:29am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/5 "2004-10-29T04:29:02Z")
We might also consider that nervous impulses don’t move all that quickly (on the order of meters/second). How big can our brains get before speed becomes a limiting problem? We can be super-smart, or quick, but not both. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [October 29, 2004, 4:33am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/6 "2004-10-29T04:33:11Z")
We must consider the possibility that human _heads_ are getting larger, as we seek to mate with smart people and a correlation between smartness and head size is perceived. As a result, in four generations tops, pregnant women will explode in their eighth month. ---
**Author:** ![rackensack](https://avatars.discourse-cdn.com/v4/letter/r/e5b9ba/32.png) [@rackensack](https://boards.straightdope.com/u/rackensack)\ **Post date:** [October 29, 2004, 7:04pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/7 "2004-10-29T19:04:25Z")
> [@Bryan Ekers](#): > > As a result, in four generations tops, pregnant women will explode in their eighth month. Four generations? Eighth month? Heck, my wife exploded at me starting in her first month during each of her three pregnancies 😃 ---
**Author:** ![t-keela](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@t-keela](https://boards.straightdope.com/u/t-keela)\ **Post date:** [October 29, 2004, 8:29pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/8 "2004-10-29T20:29:30Z")
To say that brain size isn’t a determining factor or indicator of intelligence isn’t exactly a true statement either. The surface area of the brain is though. The number of sulci (the grooves and ridges) in the brain increase the “surface area”. If the human brain were smoother (as some mammals are) the intelligence level would reflect it. The differences in size among human brains is relatively insignificant and not generally accepted as a determining factor in intelligence. There are several physical and environmental reasons that can be attributed to a persons intelligence. Somewhat related to the OP is correlational evidence that indicates the human brain has evolved and an increase in gyri, fissures and/or sulci is the result. Thus humans are “more intelligent” than our ancestors because of an increase in the surface area of the brain. ---
**Author:** ![t-keela](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@t-keela](https://boards.straightdope.com/u/t-keela)\ **Post date:** [October 29, 2004, 8:37pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/9 "2004-10-29T20:37:59Z")
cortical folding-The convolutions are made up of ridgelike bulges, known as gyri, separated by small grooves called sulci and larger grooves called fissures. Approximately two-thirds of the cortical surface is hidden in the folds of the sulci. The extensive convolutions enable a very large surface area of brain cortex—about 1.5 m2 (16 ft2) in an adult—to fit within the cranium ---
**Author:** ![WonJonSoup](https://avatars.discourse-cdn.com/v4/letter/w/dc4da7/32.png) [@WonJonSoup](https://boards.straightdope.com/u/WonJonSoup)\ **Post date:** [October 29, 2004, 10:31pm UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/10 "2004-10-29T22:31:43Z")
I remember reading somewhere way back that brain size in a _species_ is a decent indicator for intelligence, but not for individuals. Sounds reasonable to me. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 30, 2004, 1:36am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/11 "2004-10-30T01:36:22Z")
> [@AndrewT](#): > > it would be difficult for human brains to get significantly bigger. Babies’ heads barely fit through the birth canal as it is Perhaps a tendency to greater post-birth brain development would deal with this. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 30, 2004, 1:41am UTC](https://boards.straightdope.com/t/are-human-brains-getting-bigger/271681/12 "2004-10-30T01:41:49Z")
> [@WonJonSoup](#): > > I remember reading somewhere way back that brain size in a _species_ is a decent indicator for intelligence When comparing species, anthropolgists occasionally use the encephalization quotient, which is related to the ratio of brain weight to body weight.