Re: The ultimate cause of aging

On Mar 7, 1:36 pm, dkomo <dkomo...@xxxxxxxxxxx> wrote:

But how do you explain the fact that the dog seems to age 8 times faster
than the human if aging is simply parts wearing out? Do the dog's
"parts" wear out 8 times faster than the human's? Why? Aren't the
dog's "parts" pretty much the same as the human's? The same proteins,
cells, organs, and so on?
I read some analysis of the evolution of dogs, but I don't
remember the reference. However, I do remember a little bit relevant
to your discussion.
Both dogs and humans have evolved to keep certain juvenile traits
longer than individuals in their closest relatives (i.e., other
species in the same family or order). However, they have evolved by
different mechanisms.
Human beings are neotonous. Their developmental aging process has
slowed down, even including the development of their sexual organs.
They reach adolescence much later, and grow old much later. Their
aging has especially slowed down with regards to the ability to learn,
which is in most species of mammals basically a juvenile trait.
Neotony is characteristic of animals which undergo a large amount of
competition, in environments where the abiotic environment is rather
benign (Gould, Ontogeny and Phylogeny). Humans have to compete against
each other, the savagery of the weather is somewhat secondary.
The main juvenile trait in humans is the ability to learn, by
which I mean the maximum rate of learning. A mammal brain stops
growing by adolescence, so if the adolescence is delayed the brain
grows larger and the ability to learn gets larger. An adult human
learns at a significant fraction of the rate of an infant human,
whereas an adult chimpanzee learns at a rate that doesn't compare to
that of an infant chimpanzee. Even though the infant chimpanzee and
the infant human learn at approximately the same rate, adult humans
learn at a much faster rate than an adult chimpanzee.
Humans also live longer than a chimpanzee. The longer lifespan is
a secondary effect of the neotony. The aging process was slowed down
so that the intelligence can last longer. Of course, there is a little
feedback. A person who continues to learn all his life becomes more
knowledgeable as he grows older. So the ability to learn is greatly
enhanced by the delay of senescence. So the ratio of births rate to
death rate may increase with age in primitive human societies. An old
human knows how to avoid leapards better than an adolescent. A chimp
wouldn't benefit as much from a slowed down aging process. His chances
of being eaten by a leapard are just as great as an adult as for an
adolescent.
A dog is paedomorphic. Its aging process is speeded up. His sexual
organs age faster than his brains. A mammal brain stops growing by
adolescence, so if the adolescence is advanced the brain doesn't grow
as large and the ability to learn gets smaller.
Paedomorphy is characteristic of animals which undergo a large a
small amount of competition, in environments where the abiotic
environment is rather hostile (Gould, Ontogeny and Phylogeny). Sort of
field of bullets selection. The earliest dogs were wolves that lived
in the caveman equivalent of junkyards. There was lots of food thrown
away in garbage heaps, so the wolves didn't have to compete with each
other. The abiotic environment may have been hostile, people like to
put their garbage heaps in areas that no one would want to live. Like
areas with no water, etc. When it rained, there was probably enough
water for all the dogs, when there was a drought, they all died.
Being smart wasn't as important as getting along with the humans
who lived near by, not bothering them. Being
Dogs don't live as long as wolves. However, compared to wolves
the dog is a sexual god. Dogs reach complete sexual maturity within
two years, wolves take longer. Wolves are also much smarter than dogs,
at least as adults.

Here is where the "ultimate" explanation of aging is lacking. In order
to answer these questions we have to go into the "proximate"
explanations of aging involving physiology, biochemistry, cell biology,
molecular biology, and so forth. There are dozens if not hundreds of
proximate aging processes involved, many of which still await discovery.
The adrenal glands may be involved in neotony. I know that in the
axolytol, a neotonous salamander, the adrenal glands are slowed down.
The axolytyl grows into a superlarge tadpole and reproduces that way.
I guess the competition in it little Mexican lake caused neotony. Add
iodine, and it metamorphizes.

.

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