Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: ConfusedHermit on 23/08/2012 04:28:19
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What has determined our physical growth speed from child to adult?
Our childhood stage has numerous important developments going on in the brain (and a longer childhood has been more beneficial to our intelligence when we DO mature into adults), but does that mean everything has to be develop slowly?
Why don’t our bodies become adults faster?
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A very interesting and thought-provoking question!
Perhaps physical maturation is limited by mental maturation (ie, the ability to learn)? There's so much to learn that it would be disastrous if, say, a five-year-old had physically reached teenagehood and attained the physical ability to drive a car. As it is, little kids get themselves into plenty of trouble as little kids. In fact, so do teenagers.
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I'm no expert, but your theory does make me wonder. Does learning capacity set the speed of the growth of the body? If we were any less capable than we are, would we have had more need to become adults to survive? If we were even more capable, would we still look like children in the teen years?
Chimpanzees hit puberty at around eight to ten years and considered adults at fifteen, and most apes are very social and intelligent creatures.
Are there any exceptions to the rule (or guess) of 'smart social thing has intelligence and power of the group, has more time to develop and less pressure to become physically self-capable, and evolves to keep a longer childhood because the quality of mental development is valued more than the speed of physical?'
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If we were any less capable [mentally] than we are, would we have had more need to become adults [physically] to survive?
This sounds reasonable to me. You're saying that, for example, those of us who are much less mentally capable, may as well start an adult work career early in life rather than, say, try to attend high school and beyond. Secondary and post-secondary education would be little/no value benefit to them, and the time spent there would detract from their adult career.
If we were even more capable, would we still look like children in the teen years?
I would say not. If (and this is a big if) a child prodigy happened to have the body of an adult at, say, age 12, then along with adult intellectual and psychological maturity, the physical maturity would allow the prodigy to begin an adult work career. Otherwise, it would be like forcing an adult to do childhood things for the next six years, to which the prodigy would complain, reject, etc.
Are there any exceptions to the rule (or guess) of 'smart social thing has intelligence and power of the group, has more time to develop and less pressure to become physically self-capable, and evolves to keep a longer childhood because the quality of mental development is valued more than the speed of physical?'
I'm not sure what this means. If a society that provides/protects its young and gives them more time to develop mentally, then mental development can become a significant factor for survival. And are there any exceptions to this? I think that mental development can be a significant factor for survival for all species, but there are many species that cannot provide/protect its young to allow them to develop mentally.
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No no, what I meant was if we were less mentally capable at the dawn of humanity-- would we have had more need to become adults physically. I'm not talking about the present, since we've already evolved to grow at the pace that we grow.
We've evolved since then to keep the paces we have, but what I want to know is why that trend caught on. If it WAS mental capacity, I am fascinated by the body's priorities. It would be like saying 'Nah, it's okay. You're clever and grouped enough to put puberty and adulthood on hold for a while. Build your brain first, kiddo!'
Nature is and has always been cruel, so that idea just blows my mind if it's true :{O~
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I think you're asking that, if humans were overall less mentally capable at the dawn of humanity, would there be a greater need to physically mature more rapidly?
You specifically stress at the dawn of humanity compared to my example of today. However, I don't see a big difference as to when the situation presents itself. Yes, a more rapid physical maturation would compensate to some degree for less mental capacity overall and improve fitness for survival — in both cases, at the dawn of humanity and today. However, fitness against the environment at the dawn of humanity is more unforgiving compared to fitness within the community of today.
There's some kind of language barrier here, and I'm not saying it's on you.
Some animals are born straight into survival mode. Baby turtles hatch on beaches and make a mad rush to the sea before marauding animals (birds?) gobble them up. I imagine that other marine animals (such as tuna, squid, etc) are also born into straight into survival mode. But maybe we don't appreciate their lives enough to see otherwise.
I think it's when a species is so prosperous and highly survivable that the immature (and even adults) have time to play. I think "play" can be (or is) synonymous with casual learning as compared to the live-or-die on-the-job training. It seems to me that only mammals have reached this point in evolution. Think about it ... of all the videos that you've seen of animals at play, were any not mammals? I think we can say that some bird species have reached this point to a small degree, otherwise, the only playful animals are mammals.
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I'm sorry if I couldn't convey my idea clearly. It's something I'm working on when making threads here :]
So, are you saying we have our answer already? We can add it to the books? 'Our intelligence is why our bodies don't rush to adulthood compared to most organisms on Earth?' I Google things like that, but I haven't seen any studies on it. Could we be the first to even talk about it? That would be something!
And that's a fascinating point about mammals. You're right, I haven't seen examples of play in anything but mammals. It's interesting how some cultures associate fun with irresponsibility, and yet we (all mammals) are even capable of experiencing it because we've become so well-survived. Nothing irresponsible about that! :{D~
I wonder if certain dinosaurs played...
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Perhaps one can look at budgets, calories, and trade-offs.
Say you budget about 2000 calories a day for food
And, use about 400 calories a day to support our brain, whether it is during the lean winter months, our bountiful autumn months.
And one certainly needs "free time" to develop the brain. One can't be grazing all the time.
So, the slower growing may be a trade-off for devoting more food and resources to brain development and less for growth. Also, through a period of the childhood, the parents provide 100% of the food for the children. As it is, most children eat like little horses. Any faster growing, and it might be too much stress on the parents.
Humans may also be one of the slowest animals to learn tasks such as walking. Many animals are walking within minutes or hours of birth. Human infants are completely helpless at birth. But, the slow development may be an adaptation for the extreme flexibility we have in performing tasks. So, rather than innate knowledge of how to move our hands, the human infants all learn the basic hand movements de novo. But, doing so gives the ability to do things like reaching around objects to grab a coffee cup, or to carry the coffee cup across the room without spilling it. Or, perhaps skills such as carrying a barbell in one hand and an egg shell in the other.
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It seems our intelligence has also shifted our survival vs lifespan curve, which effects the perception of how slowly or quickly humans grow up. How shall I describe this ... intelligence affects the rate at which humanity increases its knowledge (and the width and depth of its knowledge). So, for example, over the last 100 years or so, we've seen tremendous advances in food production, healthcare (for example: infant mortality rate, fighting/curing diseases, elder care, etc), safety in the workplace, computational abilities (number-crunching, statistics, computers, etc), etc. (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.treatment-skincare.com%2FSkincare-Images%2FIS-Clinical%2FLifespan-Survival-Curve.gif&hash=ae67bf10da1ee482be99569a1b018621)