Why can some species newborns run immediately, while human newborns can’t even hold up their own heads?
This happens because of two of the most uniquely human features: * **Big brains relative to our body size** which helped with tool usage, running "what if" scenarios, etc. * **Bipedal locomotion**: which uses much less energy than walking on all fours When our bodies adapted to being bipeds, our …
The Short Answer
This happens because of two of the most uniquely human features: * **Big brains relative to our body size** which helped with tool usage, running "what if" scenarios, etc. * **Bipedal locomotion**: which uses much less energy than walking on all fours When our bodies adapted to being bipeds, our pelvis shrunk. But since our brains were also growing, natural selection favored delivering our fetuses earlier in development. Really, small infants are sort of an external fetus. Even at the current gestational period of 9 months, it's really a horrifyingly tight fit through the birth canal. Unlike other primates' pelvises, which have plenty of room, womens' pelvises get narrower at the end, and in fact the baby's head has to turn 90 degrees as it's exiting in order to fit. EDIT: ~~we're~~ were
Analysis
Key Concepts: Brains, it's, pelvises
This explanation focuses on brains, it's, pelvises and spans 129 words across 7 sentences. At 79% above the average Biology explanation (72 words), this is one of the more thorough answers in this category, reflecting the complexity of the underlying question.
What This Answer Covers
The explanation opens with: “This happens because of two of the most uniquely human features: * **Big brains relative to our body size** which helped” It then elaborates by presenting a contrasting perspective, ultimately building toward a complete picture across 7 connected points.
How This Compares in Biology
Ranked #61 of 500 Biology questions by answer depth (top 13%). This places it in the comprehensive tier — the top quarter of most thoroughly answered questions. Questions at this depth typically involve multi-faceted topics requiring nuanced explanation.
Frequently Asked Questions
Is there a simple explanation for why some species newborns run immediately, while human newborns can't even hold up their own heads?
This happens because of two of the most uniquely human features: * **Big brains relative to our body size** which helped with tool usage, running "what if" scenarios, etc. * **Bipedal locomotion**: which uses much less energy than walking on all…
How detailed is this explanation compared to similar Biology questions?
This is one of the most thorough answer at 129 words, ranked #61 of 500 Biology questions by depth. The key concepts covered are brains, it's, pelvises.
What approach does this answer take to explain some species newborns run immediately, while human newborns ?
The explanation uses root cause analysis and contrasting perspectives across 129 words. It is categorized under Biology and addresses the question through 2 analytical lenses.