All the possibilities and powers of the mature adult are contained in the DNA of the immature versions of all species, including humans. There is nothing in the non-human species that "retards" development, so all reach full and successful maturity quickly. But only in human species, all the individual examples (toddlers, the little ones) are forced, by parents first, siblings and peer groups later, to engage in, what can only be seen as "detrimental" (i.e., "retarding") mental, emotional and physical activities that require so much ordinarily refined energy from the little ones (from the simple digestion of food, air, impressions from being alive, including their attention and awareness) that they can never accumulate adequate quantities and qualities of energy (from the blood) that is necessary for that kind of "extra-ordinary development" - sometimes even called, evolved development - that any human child should be able to achieve by the age of majority, if not sooner in some rare cases.
Life requires something specific from humans, that is no longer required from all the other species because they have been here so very much longer than humans and have already reached their "fully evolved state"; that is, they are "closed-ended" nervous systems. Humans, however, are "open-ended" and still evolving in a particular way quite unknown to most, and that "something" can only be KNOWN - fully KNOWN and UTILIZED - by a few humans in any generation, maybe 1% or less, and for a very hard to detect reason.
There is such a thing as "burning oneself out" before one's time, by the overly excessive misuse of one's ordinary, genetically wired-up intellectual, emotional, and physical capacities. The "opposite" of that ("enlightening oneself up"), would be something like: RATHER THAN becoming a "jack of all trades" (though, it's usually just a few in reality of course), little humans should be taught to specialize, in order to become a Master of One, and especially of Oneself. How obvious, eh?