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Soviet writer/philosopher Ivan Yefremov (probably, the most influential soviet Sci-fi writer) argued rather convincingly, that humanss have ideal body size and
by Andrew_nenakhov 5y ago
Soviet writer/philosopher Ivan Yefremov (probably, the most influential soviet Sci-fi writer) argued rather convincingly, that humanss have ideal body size and layout for intelligent beings, and that extraterrestrial life would probably look somewhat similar.
- genesis126 5y agoGod: "I thought so too"
- TedDoesntTalk 5y agoThe article mentions that we have 4 limbs only because the creature that left the sea had 4 fins. It could easily have been 6 or 8. He makes it seem as though 4 was just plain random.
- Andrew_nenakhov 5y agoHaving more limbs is less efficient biomechanically - the creature would need a larger heart to pump blood through al organs, that requires more energy, so such creature would need more food. Now, it is known that creatures can lose limbs through evolution, but never gain them, so it is likely that multi-legged species would gradually lose extra limbs over time.
- Joker_vD 5y ago> creatures can lose limbs through evolution, but never gain them Wait, so where did the limbs come from anyway, if they could not be gained?
- Andrew_nenakhov 5y agoEarly creatures had mady different body plans. We have 4 (all vertebrates), 6 (insects), 8 (arachnids) and multilegged creatures (millipedes), as well as legless creatures like snakes (who had 4 legs before they lost them). It seems that vertebrates have certain period when this layout was 'cast in stone' [1] [1]: https://biology.stackexchange.com/posts/21793/revisions https://biology.stackexchange.com/posts/21793/revisions
- benfarahmand 5y agoReading your comment made me wonder why we have even numbers of limbs for different body plans. I realized it's due to bilateral symmetry for most organisms must some how be advantageous to asymmetric body plans, but I'm unsure how symmetry is advantageous. What are the evolutionary pressures selecting against asymmetric body plans?
- Andrew_nenakhov 5y agoI'm not really a biologist, but I think this has something to do with the balance: when you move in some direction, it would be extremely disadvantageous to have one side significantly heavier than another. Take two runners, give one a 15 kg weight in one hand, and give another 15 kg weights in both hands (30 kg total). I think the runner with weights in both hands would run faster than the one with one weight. Thus, moving species evolve to be bilaterally symmetric. If the organism has no need to move in certain direction, it doesn't really have bilateral symmetry, like trees or bushes (though big trees generally tend to have their center of mass close to their vertical axis).
- goatlover 5y agoOctopuses mange to do okay. And they seem alien enough for a related species. Cephalopods serve as a good counter to the article.
- Andrew_nenakhov 5y agoThey are aquatic species. When you remove the necessity to support weight above the hard surface, your options are much more varied. Even jellyfishes or amoebas somehow manage to get by.
- bmitc 5y agoIt's also interesting to point out that they have three hearts and not just one heart.
- TedDoesntTalk 5y ago> it is known that creatures can lose limbs through evolution, but never gain them Did spiders start with more?
- jnurmine 5y agoOne thing I've found fascinating is how the outside appearance of a human body repeats the number 5; there are 5 things sticking out from a center mass (2 legs, 2 arms and the head). Each foot has 5 toes, each hand has 5 fingers. And in the head are 5 outward-facing holes: 2 eye sockets, one nose/mouth hole and 2 ears.