Why Are Human Babies Born Helpless Compared to Other Mammals?

[Dmitry67]

You know, some mammals can walk within few minutes after birth.
And for human beings in takes few years to be able to walk.

Obviously, nature was able to 'pre-wire' our brain so we would be able to walk immediately. It would increase a chance for survival for humans. It could be a benefit BUT... but nature had REMOVED that ability. I say "removed", because more primitive beings have that ability.

So my question is, what HUGE benefits nature and natural selection got from removing that ability and from the prolongation of the period of being total helpless that had completely overweighted obvious benefits of not being absolutely helpless?

 

[mgb_phys]

<zombie voice>Brains</zombie voice>
Human babies are born about 2-3months too early compared to most other mammals, because if you waited until they were fully developed the head would be too large for them to be born.
The downside is that they are very vulnerable, the advantage is that they grow up to know how to bang rocks together.

 

[Dmitry67]

It does not explain everything.
Babies can not walk in age of 3 month.
Compare babies to Kangaroo

 

[cam875]

maybe its something to do with social interaction and bonding, humans are a very sociable and love needing species, therefore its a perfect time when your a baby to hopefully receive that instead of being an independent super baby by the age of 6 months.

 

[Dmitry67]

well, babies learn social interaction after age of 1.5 years for the next 20 years.
I don't know why babies can not walk and learn. In fact, they would learn faster.

 

[mgb_phys]

Compare babies to Kangaroo

Kangaroos are a bad example - marsuipial babies are born as very early embryos - they crawl into the pouch where they gestate.
Baby Kangaroos aren't really born from the pouch as such, they just spend longer and longer away from it - rather like a teenager no longer living at home.

Generally how long babies remain dependent on the mother correlates with the length of the pregnancy and the animals lifespan. Baby elephants also spend a long time being cared for. If it takes 1-2years to produce each new set of offspring then it is probably an evolutionarily advantage to put some effort into looking after them rather than with say rodents that can breed more quickly where it makes sense for the babies to become independent quickly to allow a new generation.

 

[TheStatutoryApe]

How many other animals learn to walk on two legs and are built for it? Walking on four legs is probably easier than walking on two and human babies learn to crawl before walking on two legs even though we are not quite built for crawling on all fours.

The female chimp has an estrus cycle of about 34 to 35 days. While in heat, the bare skin on her bottom becomes pink and swollen, and she may mate with several males. She normally gives birth to just one baby, which clings tightly to her breast and, like a human baby, develops rather slowly. An infant can sit up at 5 months and stand with support at 6 months. It is still suckled and sleeps with its mother until about 3 years of age, finally becoming independent and separating from her at about 4 years. Sexual maturity is reached between 8 and 10 years.

Apparently chimps develope at a similar rate.

 

[MissSilvy]

Babies cannot grow both their brains and bodies at the same time. When you're an infant, it's a choice of one or the other since both are HUGELY expensive in terms of energy. Our ancestors had a limited amount of energy available to them (and there's only so much you could forage in a given day as well) so you couldn't do both at the same time and expect to live. The brain growing before the body would be fatal for species that weren't extremely social and lived in codependent groups because they would die. Why not just grow the body and then concentrate on the brain? Brains develop better when they have more time to grow:

But what are the possible neurological correlates of increased brain size during primate evolution? To address this, Finlay and colleagues concentrated on critical factors that drove mammalian (including primate) brain size, especially the manner and number of neurons generated during development (Finlay and Darlington 1995, Finlay et al. 2001). They found that the longer cytogenesis is prolonged for a given structure (based on timing of the peak in ‘neuronal birthdays’), the larger the structure will ultimately be.

From http://www.anthro.fsu.edu/people/faculty/falk/Handbook_V2.htm

So to answer your question; it's better in the long term to grow brains before the rest of the body and humans, being highly social, could afford to support their infants throughout this extended childhood, which (I'm hypothesizing but I could perhaps find references) in turn produced smarter humans who would survive better and support the survival of their own infants to adulthood, and so on and so on.

 

[Dmitry67]

Thank you, interesting link

 

[Brilliant!]

How many other animals learn to walk on two legs and are built for it? Walking on four legs is probably easier than walking on two and human babies learn to crawl before walking on two legs even though we are not quite built for crawling on all fours.

This.

Walking upright is one of the greatest developments in any species that has ever existed. But, it comes with some hefty requirements. First, before we can walk on two legs, we must develop highly functioning motor skills. Measuring the difficulty of bipedal movement over qaudripedal isn't as simple as multiplying by two because we've gotten rid of two legs. To get an idea, imagine a long dining table with two legs. Where the two legs are located isn't important, although some positions are obviously better than others. What is important is that you realize that a table with two legs may be fine for novelty purposes, but is utterly useless (maybe some kids could you it as a skateboard ramp, but you probably aren't eating off it). There are several forces acting on this table, of which Gravity is the most important. With four legs, the table stands a chance. In fact, it doesn't need to concern itself with Gravity at all. However, with two legs... you get where I'm going.

Gravity: there's the rub. Perhaps we will one day evolve to a point where a woman's uterus rotates like a gerbil wheel, and babies will be able to develop their balance and equilibrium in the womb. For now, they'll just have to deal with it when they're born.

 

[Moonbear]

Animals that are prey, or that have parents that abandon them quickly, tend to be more precocious at birth...they need to be able to run quickly or they become a midnight snack.

Those that are predators or have parents that can invest a lot of time in rearing them in a safe place away from predators, are born more altricial. So, even rats are born very altricial, because they are in burrows away from predators.

 

[xxChrisxx]

Perhaps we will one day evolve to a point where a woman's uterus rotates like a gerbil wheel...

Now there's an image to make you stop and wonder.