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Re: Play and spikes : Phylogenetic Link? LONG

In a message dated 96-07-11 10:03:13 EDT, Martin
martin@hpentccl.grenoble.hp.com wrote:

> John Bois wrote: 
> > In most (all?) species that play, the play behavior usually relates to a 
> > skill or behavior that the organism will need in adult life.  I forget 
> > what wise person said it, but play is the _business_ of children.  I am 

I think that  John hit the nail on the head (sort of) when he pointed out the
apparent altricial/precocial dichotomy association btween animals that
exhibit play ability and those that do not. It seems to me that this
dichotomy has it's underpinninggs  at a _Taxonomic/Phylogenic_ level. In
other words, most if not all -therian mammals appear to  use play as training
for adulthood. The young of most if not all reptiles appear to _not_ be wired
for play. Is this an artifact of the reptile-mammal split of the Triassic?
What then about the Therapsids which were the intermediates between reptiles
and mammals in the colloquial t p[hylogentic sense? Play then seemd to
develop by animals with higher metabolisms, longer gestation periods and
longer times to maturity which brought on the need for long term parental
involvement. By imitating the actions of their parents, play, evolved . Again
this dichotomy is striking. Reptiles dont't play and mammals do! Moving on to
the birds( the Reptile-Aves split) both precocial and altricial. Some birds
seem to exhibit the ability to play and as John points out this trait  seems
best developed in altricial birds. Why? More direct parental involvement!
This involvement aslo imprints the behavior on the young who in turn emulate
it. Precocial birds by virtue of being hard wired from the start loose this
brain capacity in favor of being miniature forms of the adults. It seems then
from a genetic standpoint that eventhough reptiles lack the ability to play
the reptile genome served as the template for mammals and aves to evolve this
ability along with their more complex socialand metabolic strategies. Now for
dinosaurs. There is evidence for both precocial and altricial  nesting
strategies as well as possible evidence for endothermy (or homeothermy). But
being reptilian , I am inclined to believe that the dinosaurs lacked the
ability or need to be wired for play. I won't leave out the possibility that
I am wrong however. Since dinosaurs in a sense are intermediate between
reptiles and birds, (also in the Triassic) it could be just as likely that
the trait was just beginning to express itself .

> It's exactly this that I find difficult to swallow.....it seems a
> cart before the horse kind of explanation.

If you look at the problem from a phylogenetic perspective I think it becomes
more palatable ;-)  It seems to me the use of the word "play" is a semantic
one. When we think of play we tend to think of children at play. What are
these children doing? Conciously and subconciously imitating their parents
and other adults. Obviously, the lower animals do not think in the sense that
humans do. Theirs is a more subconcious attempt to emulate thieir  world.
Ther are plenty of examples. Immature bucks of any dear species imitate the
actual head butting combat of adult males. Young of the Great Cats take part
in the hunt first as passive observers then later as participants. In the
interim, they practice (play) on anything they canpounce on! Sow me any
reptile that displays this kind of behavior!
> In order to kill prey, for example, you don't need to practice as a
> youngster.  Plenty of species get by without.

Those that don't are reptiles who must fend for themselves from birth as well
as fish and amphibians. Those that do are probably  mammals and some birds.

It's all  quite simple IMHO.

Thomas R. Lipka
Paleontological/Geological Studies