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Comment by somenameforme | Hacker News Reader

One of the most curious things I learned about babies is that they are born with a walking instinct, long before they actually can walk. If you hold them up, they will move their legs in a perfectly correct walking fashion. But they lack the strength and agility to keep their body up. At around 3 months this walking instinct disappears, and then at around a year we 'relearn' to walk when we have the strength and agility to hold ourselves up.

But if we were on a planet with significantly lower gravity, humans would likely be walking very near immediately.

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One of my kids could stand on the day she was born. She seemed super strong, so while I held her I just took my hands away, and she stood there and stared at the rest of the family. Lasted a good 10 seconds, then I thought it was enough.

My boy is 2mo old and he could lock his legs with extreme strength in the first few days. I was very impressed, but my wife told me to stop letting his legs hold any weight. Apparently his uncle was walking at 9mo but his body wasn't ready and he gave himself a hernia.

Babies have strong legs in order to push themselves out of the womb

This was indeed a wrong statement - I was pretty sure I had read something along these lines, but I checked it out after writing this and no, it's not the case.

>> One of my kids could stand on the day she was born. She seemed super strong, so while I held her I just took my hands away, and she stood there and stared at the rest of the family. Lasted a good 10 seconds, then I thought it was enough.

Probably a good experience. However, at that age it may have been a setback if the kid fell down and got hurt because they weren't strong or coordinated enough. The experience (good or bad) of doing something for the first time can be very influential on future behavior.

According to my wife, who is an OT, children are born with a reflex that straightens their legs and which sounds similar to what you saw.

She said they lose the reflex during their first year, and then develop the actual skill of standing separately.

It was fun to watch with our kids, too!

Is this separate from the prenatal kicking? Or just a continuation of it?

I don’t know, it was just something she mentioned at 3am while we’re trying to put the baby back to sleep

But I think it could be!

If we were on a planet with significantly lower gravity, walking would be much more difficult. Notably, on flat ground we absolutely must have an upward component to our application of force with the surface - this is clearly seen in videos taken on the lunar surface during the Apollo missions. This baby on a hypothetical lower gravity world would find standing easier, yes, but not mobility. At least not once he's taken his first few trail steps.

The moon has very little gravity bringing extra problems, but maybe Mars would have the right gravity to enable Babies walk from the beginning?

If you enjoy this kind of speculating you might like the Expanse series of books and TV shows.

They have humans growing up on Mars, the asteroid belt, moons. Anyone who doesn’t grow up on earth cannot go there without extreme gravity training.

I did enjoy the first season of the series, but then was turned off by some story arcs, but maybe I will give it a try again. Are the books more consistent?

Much more consistent. Books are huge, hence the need to shorten them.

But IMHO, series have done a really good job overall. Given how nearly impossible it is to simulate micro-gravity, or other advanced technology.

Also, in season three or four suddenly everybody started cursing all the time. The series just wasn't fun to watch anymore.

I legitimately did not notice this and I cannot imagine it affecting my enjoyment of a show.

That series strived for realism in that regard, and in using magnetic boots to work in zero gravity; which was admirable. That made the things that were not realistic stand out even more imo. The (unfortunately named) Epstein drive, a drive that consumes very little mass under constant acceleration allows for relativistic speeds in very little time (weeks). Their ships were flying from one side of the solar system to the other in weeks, but they couldn’t make interstellar flights? Also the effects of cosmic rays and hard radiation on reproduction makes the disaffected belter population seem impossible. That’s all fine of course, just inconsistent imo.

Shohreh Aghdashloo performance was a real treat though!

She was also in a show with Ray Liotta (Smith) that, in spite of some unevenness, sadly didn't make it through its first season.

Regarding reproduction, I'm willing to write that off to advanced medical technology doing DNA repair. Most of the plot wouldn't be that different with slower space drives, so I wasn't too bothered by that either.

But fwiw, it turns out it is possible to get that level of rocket performance, if ToughSF got their numbers right:

https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr...

It wouldn't look the same and the power level would be higher than what all of civilization uses today, but the amount of fusion fuel isn't all that remarkable. The design uses helium-3, which could be collected in large quantity from Uranus and Neptune.

The Epstein drives are efficient, but not efficient enough to run for months at a time without stopping, and are thus unusable for interstellar travel. The books go into that when talking about Medina/Behemoth/Nauvoo... The whole reason it had a rotating drum was because the engines would only be active at the start and end of the journey.

Walking would probably suck on such a planet and we would see babies bounding long distances instead!

If gravity were lower we would have evolved differently, walking would have adapted too. On the other hand babies probably wouldn't be able to walk either. Being mobile, defenseless, and not having "runaway!" as the default defense mechanism (like horses) is an evolutionary dead end.

Sure we might have evolved differently. But that doesn't mean that the human body doesn't work better at sustained 0.8G or 1.2G or whatever.

Problem is we don't have any good data about which gravitational accelerations would be suitable for long term health. We have 1g as our baseline, and we know that months in 0g messes you up and longer is a bad idea. We don't know anything about the long-term effects of living in Mars or Lunar gravity though. It could be studied using von Braun stations, but nobody has done it.

IIRC they also have a swimming/diving instinct/reflex, which they similarly seem to unlearn after a while.

Infants will also grip anything you place in their hands.

They will also grab with their toes. Place your finger across their toes between the foot and the sweet little toesies and they will grip your finger pretty hard. We monkey

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