In evolutionary terms, why people living in high latitude became bigger and taller?

Question

while people living in low latitude people became shorter and smaller.

is it because the shorter the better the heat dissipation and vice versa? explain me why smaller is good for dissipation and bigger good to hold heat?

Answer 1

This is nothing to do with evolution.

It is Natural Selection acting on genetic variation occuring naturally within the pre-existing gene pool.

Evolution (molecules to man) requires a net increase in genetic information. This has never been observed.

Answer 2

That's not exactly the case. In colder areas people have less surface area compared to overall mass, so they end up stockier with shorter limbs, like the Eskimos.

Africans, even pygmies, show a very long limb length compared to their height. The crucial measurement is the 'crural index', the ratio of femur to tibia.

these two links have some useful info stashed on them..

http://64.233.183.104/search?q=cache:mTZ...

http://books.google.co.uk/books?id=L9djD...

This is the crural index of some modern populations. As you can see from the numbers, the hotter the climate the longer the limbs.

Lapps               79%        .25

modern Inuit        81.5%     4

Belgium             82.5%    10

S.African white     83.2%     8.5

Yugoslav            83.75%    8.4

American white      82.6%     9.8

Kalahari Bushman    83.4%    18

New MexicoIndian    84.6%    14

S.African black     86.4%    17

Arizona Indian      85.5%    18

Melanesian          84.8%    23

Pygmy               85.1%    24.2

Egyptian            84.9%    26.1

American Black      85.25%   26

Answer 3

People in high latitudes are not necessarily  taller, but they do have more bulk because of the need to conserve body heat.  Heat is the enemy of those living in tropical areas, so they tend to have a more slender build & longer limbs.  A slight build or long limbs would be a disadvantage in colder climates.

Answer 4

Just a guess but I think it has something to do with how much oxygen we take in. Bigger people would have a bigger lung capacity.

Answer 5

Actually, at the highest latitude, it's advantageious to be short and stocky, as the less surface area you have, the better you preserve body heat.

Thus, Eskimoes and people in northern Asia tend to be short and stocky.

If you live near the Equator, your body doesn't need to retain heat, but dissipate it. Thus, some of the tallest, slenderest peoples are equatorial.

Answer 6

--------------As for the first question, I shall leave it to someone else. Let me just try responding to the second, why smaller is good for dissipation and bigger good to hold heat----------------

I know there was a science article dealing with the math; gotta hurry out, so I'll give it in a nutshell. Perhaps someone can dig it up for you.

notation: I shall denote "is proportional to" by "=8=".

body heat =8= body mass (basic metabolism)

heat dissipation =8= (temperature gradient) x (surface area)

let's say r1 = height quotient for short person

and r2 = height quotient for tall person

(assuming they are roughly equal in bodily proportions)

let us further say r1 x 1.414 = r2

that is if the shorter guy is 141.4 cm tall, then the tall guy is 200 cm tall.

Let us also assume atmospheric temperature outside is the same, say 5 degrees centigrade for both.

rate of heat dissipation =8= body surface/heat that will be dissipated =8= (r^2)/(r^3)

(because surface area =8= rate of heat dissipation

and also heat to be dissipated "is inversely proportional to" rate of heat dissipation)

The rate of heat loss for short guy =8= (r1^2)/(r1^3) = 1/r1

The rate of heat loss for tall guy =8= (r2^2)/(r2^3) = 1/r2

The ratio of rate of heat loss between the two

tall guy : short guy

= 1/r2 : 1/r1

(but we had assumed that r2=1.414 x r1)

=1/1.414r1 : 1/r1

=1 : 1.414

The shorter guy will lose body heat 1.414 times faster than the tall guy assuming everything else remain identical (or proportional in 1 dimension)

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It was something like that. Shorter guy cools a lot faster; better in warm to hot weather, but fatally disadvantaged in extremely cold weather.