In This Thread I ponder the feasability of developing breeds of humans in much the same vein as dogs are bred into wildly differnt physiques and temperaments.
Seems like the primary impedement to doing this involves what seems to be an absurdly long delay of sexual maturity in humans. What is the principle cause for this defecient fecundity? Evolutionarily, do humans realize substantial gains in delaying reproductivity?
Cattle, much larger than humans, attain repproductive age between 3 - 4 years. Gorillas, arguably more closely related to humans than are cattle, reach sexual maturity at about 7 years. Why does the wimpy, wispy human double that delay, and what can be done to return human fecundity to a more reasonable onset?
Grrrph. Sort of like those really tame Russian farm foxes maturing with their puppy fur patterns? Hmm…now I must do some research and determine if there is a correlation between furriness, diminished brain pan, psychoses and fertility ages. This one may yet prove to be a tough nut to crack.
First off, human babies are born “pre-mature” by about 1 year. Like our primate cousins, we experience a period of rapid brain growth in the last stages of pregnancy. Unlike them, however, our brain growth doesn’t slow down at birth-- it continues at the fetal growth rate for about 1 year. Secondly, it shouldn’t be all that surprising that we’ve extended the pre-sexual maturation years beyond our ape cousins, just like the apes have extended theirs beyond our monkey kin. The problem with tinkering with sexual maturation dates is that you probably couldn’t do it w/o also affecting what makes us uniquely human.
Would a species of human-like beings that reaches sexual maturity and starts reproducing at age 5 be at all similar to us in an overall sense? What makes humans an effective species is hopelessly intertwined with the fact that it takes us a very long time to mature and reproduce. That includes physical, developmental, and social attributes. You can’t separate out the question without making the question a pure hypothetical.
Well, ideally, from a breeder’s perspective, they are (were). Or at least they’d have been upon her when she passed away.
I’m not quite sure I’m making the connection between humanity and delayed reproduction. I get that it takes a few years (usually between 10-15) for humans to get a firm grip on socialization and to learn to harness and master their brains to the full potential of the organ, but why would halving, or even quartering physical maturity compromise that development?
If one were to start a breeding program by developing a human stock that was full-grown and could sucessfully reproduce within 5 years, would the result necessarily be simian in appearance and temperament? Would capacity for human-like sentience and brain-power necessarily be halted at age 5? Is there a breakable link between complete physical development and mental aptitude?
Certainly, there is limited data to draw on with regard to humans, but what has been seen in other bred species?
Right now we wouldn’t know how to “speed things up” without potentially bypassing some critical developmental milestones in the brain. We know that the brain is much more maleable up until the age of puberty. In particular, something about our ability to process language changes with puberty, and I can’t think of any trait that makes us uniquely human more than language does. But there are many other milestones, too, including an ability to think logically thru a problem.
At age 5 – heck, at age 13 – most humans have not yet developed mentally to the point where they are really able to take care of themselves. Well, maybe by 13 or so in a hunter-gatherer society. At age 5? No way. There is so much mental development yet to occur that if the brain stopped developing at age 5 you would not have a human being; you would have a rather smart but incompetent ape. It would not be able to do the normal ape things that a 5-year-old chimp can do, nor would it be able to do adult human things.
One of many major differences is that the relatively late puberty in humans permits the brain to keep growing and developing for 10 more years. Many normal 5-year-olds, for example, are not really ready yet to grasp the basic idea of marks on paper being the equivalent of language. Certainly they are not able to grasp more than the most basic arithmetic concepts.
Puberty is the time when most of the brain begins to “set,” if not like concrete, at least like jello. Delaying it until the teens permits it to grow and develop longer.
I can’t imagine a 5 or 6 year-old being able to adequately care for a newborn baby.
As others have pointed out, part of the process of “growing up” is learning the skills necessary to survive in the world and to make appropriate decisions. Animals are able to do this in shorter time periods because their skill sets are not nearly as complicated as those of humans.
Even in our society today we can see what happens when young teens and even pre-teens start experimenting and wind up having children. The results are seldom good either for the new parents or the resulting children.
Does puberty cause the brain “set” or does it just happen concurrently? Does the information we have on other breeding stock preclude significant mental development beyond puberty?
Looking at adult dogs as being locked into a state of persistent “wolf puppy” suggests this link, but is it necessarily so?
A stock that can attain reproductive age in about 30-40% of the time required by its original ancestry, and yet continue to develop mentally to between 60 - 100% of the original mental capacity would be acceptable. The end result of course being a basic utilitarian thrall whose importance will be more focused on its physical utility as opposed to its humanity. After all, there is a reason we don’t use full-blooded wolves to guard our homes and protect our flocks. The breed itself would not necessarily need to be able to rear its own offspring, in fact it might facilitate culling and selective breeding if this step were eliminated.
So what would be the point of selectively breeding a subset of “humans” who were unable to rear their own offspring? Our own domestic animals, while not as sly and clever as their undomesticated relatives, can certainly raise their own babies satisfactorily.
Here’s another issue to keep in mind. There are two basic kinds of reproductive strategies: Quality and Quantity. Call them Q1 and Q2. An oyster is at the far end of Q2; it creates gazillions of offspring, cares for them not at all, and few of them reach maturity. A gorilla is at the far end of Q1. She usually has only one baby at a time, and does not have another one for several years, until the first one can care for itself. She makes a huge investment in each baby. Humans actually are an interesting compromise. Being fully bipedal, and pair-bonding, we are able to be as Q1 as a gorilla, but to give birth more frequently. However, if we space children too close together, we end up not giving enough Quality care to them, and many will die, especially in natural conditions.
There would be little or no point to maturing earlier, since we already are quite fecund enough. Last time I looked around, there was no shortage of homo saps.
The evolutionary advantage of the extraordinarily prolonged childhood-dependency period is that it means each individual has acquired an immensely larger portion of their mind-contents from caregivers. It means that our species’ thoughts and perspectives and so on mostly change over periods longer than the lifespan of the individuals who carry and edit them. It makes the acquisition and development of incredibly complex concepts a lot more likely and pragmatically useful.
BTW, the neoteny thing isn’t just that we’re born premature, it’s also that some aspects of what would be maturity in other primate species never hits us at all, or does so only over a very long period of time instead of by or shortly after birth. (Our foramen magnum openings don’t realign towards the back of our heads at all; as old men some of our males get more body hair than most of the species but even then hardly ever get as fuzzy as chimps and gorillas and monkeys; etc)
The usual terminology is K-strategy for Q1, and r-strategy for Q2. Large, long-lived animals, such as humans, tend to be K-strategists to varying degrees. K-strategies predominate in stable, predictable environments. You can even see that in different human cultures- compare the number of children that women in third-world countries with high infant mortality tend to have or want to have with the number that women in developed countries with low infant mortality have. A K-strategy makes more sense than an r-strategy in a culture where a child will need a high school or college education to be able to support themselves. Those same selective pressures tend to encourage people to start having children later- you need a lot of resources to bring up a child, so you wait until you have them.
Putting a few humans into a very unstable environment (with high infant and overall mortality) for a few thousand years might do it. But you’d have to make sure that the humans in question couldn’t modify their environment to be more stable- and that’s something humans are pretty good at doing, especially in the long run.