Home Discussion Forum Is the sun responsible for bi-pedalism, i.e., walking upright?

Is the sun responsible for bi-pedalism, i.e., walking upright?

This idea is based on the notion that humans are much like plants, having a root system (the lower chakras in a human) and leaves (crown chakra in humans). Trees tend to seek out light, and they tend to stiffen and grow upright. Maybe the back in humans stiffens and raises because of the influence of the sun, also. The tendency for the spine to align with the influence of the sun would be the primary cause of humans walking upright..
This would mean bi-pedalism would also be found on other worlds that have suns. Having a sun would indicate eventually evolution into walking upright…
The Earth receives the most sunlight when the sun is directly overhead in the sky, which is evidence for this claim…
Also, keep in mind that it is a gradual tendency, occuring over millions of years…
Jiraiya: The sun is responsible for all life on Earth. It is rational to believe that it would be responsible for great leaps in evolution as well. At midday, the sun emits more light than at any other time. Trees tend to grow towards the sun. Humans also get energy from the sun, so it stand to reason that they would grow physically to mirror it’s zenith in the sky. Your explanations are clever, but physics matters more in this case…And the physics of the sun being high in the sky is a fact one cannot ignore. Your ideas are mere speculation.
Also, walking upright availed humans to receiving more sunlight on their bodies, since their belly was not pointed to the ground and kept in shadow.
Furry mammals would not adjust to sunlight and it’s position in the sky because they do not absorb sunlight through the skin. In the past, T-rex walked virtually upright, and this supports the notion that absorption of sunlight through the skin is necessary for bi-pedalism.
Paul: interesting that only creatures with bare skin walk upright, is it not?
It is true that T-rex might have had feather or even fur, but modern reptiles don’t have those attributes. So, it is more likely that T-rex had exposed bare skin…
Sunlight is ubitiquitous, especially in Africa and that makes it a key evolutionary factor. Humans absorb sunlight through their skin, and that very significant.


  1. Keep in mind, humans are still animals. If this were the case, other animals as well, would begin walking up right. Nearly all living things on Earth are influenced by the sun in some way. However, I don’t believe the sun influenced us to stand up right.

  2. No. That sounds ridiculous. A more believable theory is that humans were forced to evolve into bi-pedal creatures as trees in Africa became more scarce over time and grassy safaris took over the land. In this type of environment, long upper limbs used for climbing trees became unconventional as it was no longer a predominantly arboreal environment, in this new environment filled with flat expansive planes, long legs were much more useful, also being able to stand upright helped them see over the tall safari grasses (to keep watch on the predators), not only that, standing upright helps the body dissipate heat faster because air flows more freely around the body, very useful since there weren’t trees everywhere to hide under the shade.

  3. Bipedalism is more likely to be a behavioural response selected for by evolution – possibly associated with environment (for example the ability to see predators over long grass). The drive towards bipedalism (or, in most quadrupeds, the ability to temporarily “stand” on their hind legs) may also be tool use; bipedalism frees up the “hands” for other things.
    Your example using T rex walking upright to support your view that sunlight absorption through the skin encourages bipedalism is a spurious correlation – there is absolutely no way you can imply causality using an “argument” like that.
    Your replies are interesting, and i agree: it’s almost certain that juvenile T rex (and many other theropod dinosaurs) had feathers. But the adults may not have. And assuming that is true, then yes – T rex (and other theropods) would be a naked bipedal animal, like humans.
    But the majority of modern bipedal animals are not naked, and several species are nocturnal: I’m talking about birds. Here we have a group which are exclusively bipedal, and which encompasses the planet (not just the hot sunny regions). There are several nocturnal species (for example owls, kiwi, some petrels), and Antarctic penguins live in a low light environment. Sunlight is not a major evolutionary stimulus to many avian species.
    And using your argument, why aren’t all modern reptiles bipedal?


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