The saying goes: "form fits function". This is one of the reasons why the human femur is larger and thicker than the humerus. If humans were to walk on "all fours" (like a dog or a cat), how might we expect our bone sizes to evolve

Our superior extremities would have grown more larger but not thicker than ourselves.

Explanation: We haven't to use our superior extremities to move. But if humans were to walk on "all fours", we expect our bone sizes to evolve as form fits function

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explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.