# Why is man (about) 6 feet tall?
**URL:** https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002
**Category:** Factual Questions
**Created:** [April 19, 2005, 3:57am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002 "2005-04-19T03:57:48Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@CaveMike](https://boards.straightdope.com/u/CaveMike)
#### Post date: [April 19, 2005, 3:57am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/1 "2005-04-19T03:57:48Z")
Is there a biological reason that humans are the size that they are – as opposed to say, the size of an amoeba or a brontosaurus? Was it just luck-of-the-draw? Or perhaps based on the size and complexity of cells? Would it have been possible that all plant and animal life could have evolved ten times larger?
---
### Author:  [@Blake](https://boards.straightdope.com/u/Blake)
#### Post date: [April 19, 2005, 5:34am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/2 "2005-04-19T05:34:25Z")
We are the size we are because what we are is largely deifned by the size we are. Make sense?
Seriously. If we were the size of an amoeba we couldn’t be mammals, much less human. It’s as simple as that.
On more sensible size scales we couldn’t be cat sized because we owe our existence in large part to out hunting prowess, and something much smaller than us just couldn’t have become top predator in Africa. You only need to look at African wild dogs to see that. They’re good hunters but even in a pack they are no match for a pack of lions of hyaenas. Even with the use of tools we needed to be at least 3 feet tall to live up to the potential of our intelligence.
At the other end of the scale we need to remain upright to remain human. There are absolute limits to how big an upright biped can get, and it’s not even close to bronto size. Maybe cow size at best. Event he big bipedal dinosaurs like the Allosaurs generally held a horizontal rather than upright gait. Moroever they could work around a lot of problems by strengthening the pelvis. That’s OK if you lay eggs a few inches long but not a realistic option when you give birth to well-formed live young.
So how big and small can humans get? There’s not all that much range within H. sapiens, but that’s not surprising because we are all heavily inbred. However we can get a good idea of the workable size ranges by looking at our close relatives. These species were anatomically human form the ears down and skilled tool users so they give a very good idea of what we could be if we had to be.
One subspecies of Homo erectus stood around 9 feet tall and weighed in at around 800 pound. To put that in some sort of perspective a male gorilla weighs in at about 400 pounds. So we could put that near the top of our hypothetical human weight range.
At the lower end are the Hobbits, H. floresiensis. These people stood about 3 ½ feet tall, probably a couple of inches taller for the males. They weighed in at about 55 pounds. That defines the bottom of our human size range.
So the human species, within physiological constraints, could conceivably range anywhere from 3.5 feet and 55 pounds to 9 feet and 800 pounds. Those are probably close to the absolute limits at which a species can support a large brain, complex social structure and upright posture. We could probably get bigger or smaller if we dispensed with any of those traits but then we’d no longer be human any more.
> [@](#):
>
> Would it have been possible that all plant and animal life could have evolved ten times larger?
Nope. Plants are restricted in size to how high you can draw a column of water up a narrow pipe using just evaporation. They have come very close to that limit already. If plants had evolved some sort of heart they could probably get much larger, but then they wouldn’t be plants as we know them.
Similarly animals are restricted by the need to move. Every step taken on land puts stress on the bones and the larger the animal the more stress results. Elephants are so lage that they seriously risk breaking a leg if they run. They can’t afford to lift all legs off the ground at the same time. Brontosaurs probably had to keep three legs on the ground at all times or risk serious injury.
Ten times larger than current known limits simply isn’t feasible.
---
### Author:  [@picker](https://boards.straightdope.com/u/picker)
#### Post date: [April 19, 2005, 6:50am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/3 "2005-04-19T06:50:53Z")
I have nothing to add to this thread. I just wanted to pop in and tell you, **Blake** , that I really appreciated your well-written and intelligent response.
Thank you **f** or fighti **n** g my ign **or** ance, my frien **d**.
What about the cetaceans?
---
### Author:  [@Marley23](https://boards.straightdope.com/u/Marley23)
#### Post date: [April 19, 2005, 6:55am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/4 "2005-04-19T06:55:47Z")
> [@picker](#):
>
> What about the cetaceans?
They can get a lot bigger because they live underwater. Helps with that whole gravity thing.
---
### Author:  [@aruvqan](https://boards.straightdope.com/u/aruvqan)
#### Post date: [April 19, 2005, 7:50am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/5 "2005-04-19T07:50:12Z")
Men are about 6 feet tall so they can get the stuff on top of the fridge down for me when I ask them to=)
---
### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [April 19, 2005, 8:32am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/6 "2005-04-19T08:32:33Z")
There are certain things that work well for us (or _have worked well_) because of the approximate scale we exist at; notably
Flint; if we had been much smaller, it would have been much more difficult to wield enough force to fabricate stone tools; if we have been much larger, it would have been difficult to find flint nodules of a size we would consider useful.
Fire; really small campfires simply _don’t work_ - very small fires tend to merely smoulder, very large ones tend to _blaze_ and quickly exhaust their fuel.
Metals; sort of related to fire - if we were the size of ants, we’d have a really hard time refining metals; due to a number of factors:
-Molten metals have a fair bit of surface tension and would be difficult or impossible to pour (when casting) in very small quantities.
-Very small pieces of metal would not retain heat for very long at all, making the blacksmith’s job impossible.
-Scaling - a hammer that weighs 10g is not going to deform a 1mm bar in the same way as a 1kg hammer deforms a 100mm bar - the mass scales proportional to the cube of the size.
-Method of working; a human can exist more or less comfortably one body-length away from a billet of red-hot steel; an ant would be fried at one body-length from a (scaled down) billet of red-hot steel. If you can’t get close to the workpiece, how are you going to shape it?
None of these problems are insurmountable (although some of them would be difficult to overcome from a position that didn’t already have some kind of technology), but they (and there are a lot of others besides) represent a sort of statistical region in which technological existence is easier in comparison to adjacent regions.
---
### Author:  [@mittu](https://boards.straightdope.com/u/mittu)
#### Post date: [April 19, 2005, 11:26am UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/7 "2005-04-19T11:26:03Z")
> [@](#):
>
> One subspecies of Homo erectus stood around 9 feet tall and weighed in at around 800 pound.
What happened to this subspecies? It sounds to me like a formidable predator so why did it become extinct? Was it a matter of not being able to catch enough food to fuel such a large mammal?
---
### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 19, 2005, 1:32pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/8 "2005-04-19T13:32:00Z")
> [@](#):
>
> One subspecies of Homo erectus stood around 9 feet tall and weighed in at around 800 pound.
They were very popular…
---
### Author:  [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)
#### Post date: [April 19, 2005, 2:06pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/9 "2005-04-19T14:06:01Z")
> [@mittu](#):
>
> What happened to this subspecies? It sounds to me like a formidable predator so why did it become extinct? Was it a matter of not being able to catch enough food to fuel such a large mammal?
Total herbivores.
No predation at all.
---
### Author:  [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)
#### Post date: [April 19, 2005, 2:17pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/10 "2005-04-19T14:17:04Z")
This subject was in the news recently. I couldn’t find the exact article but this addresses some of the same issues.
[Cite](http://www.signonsandiego.com/news/science/20040908-9999-1c8lifesize.html)
---
### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [April 19, 2005, 2:32pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/11 "2005-04-19T14:32:25Z")
Certain forms of predation aren’t so easy for larger animals; strength increases approximately proportional to the cross-sectional area of your muscles, mass increases proportional to their cubic volume (this is one of the main reasons that ants can lift many times their body weight and that whales are able to be so large).
If you’re huge, ambush predation might work, as would a sort of slow-motion chase after a similarly large and sluggish prey animal, but chasing after the little guys may be unproductive - they can change direction quicker than you and accelerate faster (even if their top speed might be slower).
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [April 19, 2005, 3:42pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/12 "2005-04-19T15:42:12Z")
> [@Blake](#):
>
> One subspecies of Homo erectus stood around 9 feet tall and weighed in at around 800 pound.
I’ve seen something about this on one of the quasi-scientific TV shows recently, but I’ve never encountered it in the literature. I’m not sure if the TV show had these guys at 9 ft and 800 lbs-- I think it was more like 6 1/2 ft tall and stockily built, which would still be considerable larger than any modern population.
At any rate, can you refer us to some literature on the 9 ft 800 lbs Erectus subspecies? Sounds a bit more like [Gigantopithicus](http://en.wikipedia.org/wiki/Gigantopithicus) to me…
---
### Author:  [@Gaius.Cornelius](https://boards.straightdope.com/u/Gaius.Cornelius)
#### Post date: [April 19, 2005, 4:51pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/13 "2005-04-19T16:51:15Z")
It seems to me that human beings are defined by their brains; if we did not have brains of sufficient capability then we would not be human - and of course we would not be asking such questions.
There must be a minimum size, weight and energy requirement for a human brain and I would guess that human bodies are at about the **minimum** size required to give birth to infant human brains, carry them about and feed them.
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [April 19, 2005, 5:00pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/14 "2005-04-19T17:00:59Z")
OK, now I remember. It was a National Geographic show called [Ultimate Survivor](http://www.nationalgeographic.com/channel/ultimatesurvivor/index.html). They refered to a “Goliath” species, \* H. heidelbergensis\*, that was over 6 feet tall. I’m going to be very surprised if there was a \*Homo \*species that was 9 feet tall, 800 lbs. Cool, if true, but I’ll be very surprised.
---
### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [April 19, 2005, 7:10pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/15 "2005-04-19T19:10:35Z")
> [@John Mace](#):
>
> At any rate, can you refer us to some literature on the 9 ft 800 lbs Erectus subspecies? Sounds a bit more like [Gigantopithicus](http://en.wikipedia.org/wiki/Gigantopithicus) to me…
I believe he is referring to [_Homo erectus palaeojavanicus_ (formerly _Meganthropus_)](http://en.wikipedia.org/wiki/Meganthropus). One would think such a gigantic hominid would have to have a particular niche in order to maintain its substantial size (the similarly sized grizzly bear spends most of its time foraging for food) and might have other issues resulting from the massive weight on a bipedal skeletal structure, but apparently it did evolve. Whether it exists today as sasquach or yeti is a question that bears asking, but the lack of substantial evidence despite decades of research (along with much deliberate hoaxing) makes it seem unlikely, though not nearly as much as the Aquatic Ape Hypthothesis.
As for the OP, consider the fact that prehistoric humans probably did not reach 6 feet in height (this is partially a result of greater childhood nutrition), and among modern human populations 6 feet is rather taller than average. Much of our current healthy development is due both to our own nutrition and that of parents, plus some geographically-imposed selective breeding. One can make a case for surface area in proportion to body mass (arguing that people in colder climates should be taller and larger for proportionally less skin area) but the heat transfer calculations don’t really make sense, and in any case humans who expanded into these areas invaribly outfitted themselves with the skins of other, better adapted creatures. There are so many factors–genetic, congenital/natal, and developmental–that go into determining height that trying to reduce it to a model with a few simple, tabulated factors is probably going to miss some pretty significant considerations.
Stranger
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [April 19, 2005, 8:06pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/16 "2005-04-19T20:06:31Z")
> [@Stranger On A Train](#):
>
> I believe he is referring to [_Homo erectus palaeojavanicus_ (formerly _Meganthropus_)](http://en.wikipedia.org/wiki/Meganthropus).
Interestingly, though, a google search of either name turns up many different sites, but all are word-for-word identical to the Wikipedia article. That leaves me somewhat skeptical. I need to spend some time on this one…
---
### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [April 19, 2005, 8:51pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/17 "2005-04-19T20:51:11Z")
> [@John Mace](#):
>
> Interestingly, though, a google search of either name turns up many different sites, but all are word-for-word identical to the Wikipedia article. That leaves me somewhat skeptical.
Could be that it’s a hoax or a misunderstanding. Biomechanical considerations make it difficult to conceive of a gigantic hominid in absence of some extreme adaptive pressures–our current stature and skeletal configuration is highly compromised as it is–but it’s not totally outside of conception. As an analogue, consider the genus _Giraffa_ with their extraordinary long necks and all adaptations required to maintain their height (oversized heart, stretched vertebre, extended musculature, et cetera.) An evolutionarially unlikely beast, but one that found a successful niche for itsself in a highly competative ecosystem.
Stranger
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [April 19, 2005, 9:04pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/18 "2005-04-19T21:04:54Z")
> [@Stranger On A Train](#):
>
> Could be that it’s a hoax or a misunderstanding. Biomechanical considerations make it difficult to conceive of a gigantic hominid in absence of some extreme adaptive pressures–our current stature and skeletal configuration is highly compromised as it is–but it’s not totally outside of conception.
You’re right, it’s not. My skepticism comes from two sources. 1) I do a lot of reading to keep up to date on hominid evolution, and I’ve never encountered this species in the literature before and 2) as I said above, the only cites that turn up from a google serach are all word-for-word identical.
I’d need to see something beyond the Wiki article (and its various clones) before I’d be ready to say this is legit.
---
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [April 19, 2005, 9:48pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/19 "2005-04-19T21:48:00Z")
Geez, maybe if actually read the whole Wiki article I would have noticed this gem (emphasis added):
> [@](#):
>
> Meganthropus is a good example of the great variation that existed in the Homo erectus line that is only equalled among representatives of the Homo genus by the similar variations found in modern humans. **Its remains were discovered in Indonesia and in Australia** where another subspecies of Homo erectus, Homo erectus soloensis, has also been discovered.
Anyone who claims to have found _H. erectus_ in Australia is making an extraordinary claim that simply is not generally accepted by the scientific community.
---
### Author:  [@SandyHook](https://boards.straightdope.com/u/SandyHook)
#### Post date: [April 19, 2005, 11:07pm UTC](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002/20 "2005-04-19T23:07:34Z")
> [@](#):
>
> 1. I do a lot of reading to keep up to date on hominid evolution, and I’ve never encountered this species in the literature before and
I have read about them, but only in Phillip Jose Farmer’s “River World” series. The whinney-ass Mark Twain had one named Joe Miller as a friend and protector.
[Next page](https://boards.straightdope.com/t/why-is-man-about-6-feet-tall/300002.md?page=2)