# evolution...

**URL:** <http://discourse.iapct.org/t/evolution/13742>\
**Category:** CSG2000\
**Created:** [December 17, 2000, 2:12am UTC](http://discourse.iapct.org/t/evolution/13742 "2000-12-17T02:12:40Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![Abbott\_Bruce](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/a/eb9ed0/32.png) [@Abbott\_Bruce](http://discourse.iapct.org/u/Abbott_Bruce)\
**Post date:** [December 17, 2000, 2:12am UTC](http://discourse.iapct.org/t/evolution/13742/1 "2000-12-17T02:12:40Z")

</div>

[From Bruce Abbott (2000.12.16.2110 EST)]

> Mary Powers 2000 12.16 --
> 
> Surely there is some reasonably nice way for people to say they disagree  
> with Chris Cherpas.
> 
> Not saying anything at all would do for starters.

To whom do you refer? And to which of Chris's posts? I'm afraid I haven't  
noticed anything on CSGnet that might have elicited your condemnation.

Bruce A.

---

<div class="post-metadata">

**Author:** ![Bill\_Powers1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/8e7dd6/32.png) [@Bill\_Powers1](http://discourse.iapct.org/u/Bill_Powers1)\
**Post date:** [December 17, 2000, 11:55am UTC](http://discourse.iapct.org/t/evolution/13742/2 "2000-12-17T11:55:58Z")

</div>

[From Bill Powers (2000.12.17.0453 MST)]

Bruce Abbott (2000.12.16.2110 EST)--

> To whom do you refer? And to which of Chris's posts? I'm afraid I haven't  
> noticed anything on CSGnet that might have elicited your condemnation.

Funny thing. Nobody sees anything wrong with his own remarks. Could that  
possibly be explained using PCT?

Best,

Bill P.

---

<div class="post-metadata">

**Author:** ![Abbott\_Bruce](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/a/eb9ed0/32.png) [@Abbott\_Bruce](http://discourse.iapct.org/u/Abbott_Bruce)\
**Post date:** [December 17, 2000, 12:43pm UTC](http://discourse.iapct.org/t/evolution/13742/3 "2000-12-17T12:43:02Z")

</div>

[From Bruce Abbott (2000.12.17.0740 EST)]

> Bill Powers (2000.12.17.0453 MST) --
> 
> Bruce Abbott (2000.12.16.2110 EST)
> 
> > To whom do you refer? And to which of Chris's posts? I'm afraid I haven't  
> > noticed anything on CSGnet that might have elicited your condemnation.
> 
> Funny thing. Nobody sees anything wrong with his own remarks. Could that  
> possibly be explained using PCT?

My \_own\_ remarks? Bill, I made a one word reply ("no") to Chris's evolution  
post a couple of days ago. I haven't referred to it since. Hardly grounds  
for complaining that Chris is getting unfair treatment.

Mary said:

> Surely there is some reasonably nice way for people to say they disagree  
> with Chris Cherpas.

> Not saying anything at all would do for starters.

This implies that folks have been using some rather nasty ways of saying  
they disagree with Chris. In fact, so far as I am aware, nobody has been  
saying anything at all, expecially not in the couple of days preceding  
Mary's remark, which just comes out of nowhere, with no context to support it.

Which is why I'd like Mary to explain her remark. Let's stop beating around  
the bush.

Bruce A.

---

<div class="post-metadata">

**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 20, 2000, 11:34am UTC](http://discourse.iapct.org/t/evolution/13742/4 "2000-12-20T11:34:34Z")

</div>

[From Chris Cherpas (2000.12.20.0330 PT)]

I appreciate any/all of the recent posts about evolution  
that were intended to illuminate. There are two, related,  
points that I think are relevant to PCT:

1) The size of the brain in the lineage leading to humans appears  
&nbsp;&nbsp;&nbsp;&nbsp;to have tripled between 2 million and 100,000 years ago.

&nbsp;&nbsp;&nbsp;&nbsp;Would we expect that successive layers were added  
&nbsp;&nbsp;&nbsp;&nbsp;corresponding to those theorized in HPCT, e.g., programs  
&nbsp;&nbsp;&nbsp;&nbsp;followed by principles, followed by system concepts?

2) The radical difference between the brains of humans and other  
&nbsp;&nbsp;&nbsp;&nbsp;primates is generally easier to account for on the basis of selective  
&nbsp;&nbsp;&nbsp;&nbsp;mating, rather than via physical or interspecies pressures -- if  
&nbsp;&nbsp;&nbsp;&nbsp;you disagree, I'd be interested in knowing how/why.

&nbsp;&nbsp;&nbsp;&nbsp;Assuming a (roughly) serial evolution of successive HPCT layers  
&nbsp;&nbsp;&nbsp;&nbsp;(i.e., the answer to question #1 above would be "yes"),  
&nbsp;&nbsp;&nbsp;&nbsp;what mating preferences, and corresponding references in the  
&nbsp;&nbsp;&nbsp;&nbsp;opposite sex for displaying what is preferred, would be missing  
&nbsp;&nbsp;&nbsp;&nbsp;from the current human repertoire as one strips away layers  
&nbsp;&nbsp;&nbsp;&nbsp;(i.e., system concepts, principles, programs...)?

&nbsp;&nbsp;&nbsp;&nbsp;A specific example I mentioned in a previous post was whether  
&nbsp;&nbsp;&nbsp;&nbsp;imitating successful courting would be possible without the  
&nbsp;&nbsp;&nbsp;&nbsp;system concept layer.

Best regards,  
cc

---

<div class="post-metadata">

**Author:** ![Bruce\_Gregory8](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/5f8ce5/32.png) [@Bruce\_Gregory8](http://discourse.iapct.org/u/Bruce_Gregory8)\
**Post date:** [December 20, 2000, 12:34pm UTC](http://discourse.iapct.org/t/evolution/13742/5 "2000-12-20T12:34:48Z")

</div>

[From Bruce Gregory (2000.1220.0735)]

> Chris Cherpas (2000.12.20.0330 PT)
> 
> I appreciate any/all of the recent posts about evolution  
> that were intended to illuminate. There are two, related,  
> points that I think are relevant to PCT:
> 
> 1) The size of the brain in the lineage leading to humans appears  
> &nbsp;&nbsp;&nbsp;&nbsp;to have tripled between 2 million and 100,000 years ago.
> 
> &nbsp;&nbsp;&nbsp;&nbsp;Would we expect that successive layers were added  
> &nbsp;&nbsp;&nbsp;&nbsp;corresponding to those theorized in HPCT, e.g., programs  
> &nbsp;&nbsp;&nbsp;&nbsp;followed by principles, followed by system concepts?

You are assuming that the levels in PCT are reflected by "layers" in the  
brain. I know of no evidence to support this conjecture.

> 2) The radical difference between the brains of humans and other  
> &nbsp;&nbsp;&nbsp;&nbsp;primates is generally easier to account for on the basis of selective  
> &nbsp;&nbsp;&nbsp;&nbsp;mating, rather than via physical or interspecies pressures -- if  
> &nbsp;&nbsp;&nbsp;&nbsp;you disagree, I'd be interested in knowing how/why.

You are ignoring the possibility that genetic variation might lead to a  
rapid increase in the size of the brain in the absence of selection  
pressures. In other words, a fairly simple change in the genome might lead  
to a large change in the phenotype. This can't be ruled out as far as I am  
aware.

BG

---

<div class="post-metadata">

**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 20, 2000, 3:56pm UTC](http://discourse.iapct.org/t/evolution/13742/6 "2000-12-20T15:56:17Z")

</div>

[From Chris Cherpas (2000.12.20.0740 PT)]

Bruce Gregory (2000.1220.0735)--

> You are ignoring the possibility that genetic variation might lead to a  
> rapid increase in the size of the brain in the absence of selection  
> pressures. In other words, a fairly simple change in the genome might lead  
> to a large change in the phenotype. This can't be ruled out as far as I am  
> aware.

I think selection is almost certainly involved. I don't know  
of genetic mutations that accumulate in a particular direction  
(e.g., bigger brain) without differential reproduction.

Does "no selection pressure" mean that there's never been a  
reproductive advantage in humans having a bigger brain?  
OK, if no selection were involved, then a bigger brain would  
have not improved the chances of reproducing more; but I would  
think that the individuals who kept the smaller brain would  
have a reproductive advantage because of less overhead...

Our big brain is a resource hog, using disproportionate  
amounts of oxygen, blood, and glucose (i.e., considering  
the amount of total body weight it takes). Also, the big  
brain has been one reason why babies and mothers have died  
during labor. This seems like a lot of trouble for something  
that's reproductively neutral.

Best regards,  
cc

---

<div class="post-metadata">

**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 20, 2000, 4:05pm UTC](http://discourse.iapct.org/t/evolution/13742/7 "2000-12-20T16:05:58Z")

</div>

[From Chris Cherpas (2000.12.20.0800 PT)]

Bruce Gregory (2000.1220.0735)--

> You are assuming that the levels in PCT are reflected by "layers" in the  
> brain. I know of no evidence to support this conjecture.

I am assuming you need more brain to have more HPCT levels,  
but, of course, the same sized brain could just be organized  
differently (e.g., Neaderthals had bigger brains than  
Homo Sapiens). Still, my view of HPCT is that it represents  
a vertical organization of the nervous system -- more directly  
obvious at lower (nerve-ending, spinal) levels.

The upper/outer-most layers of the brain do appear to  
be the most recent.

Best regards,  
cc

---

<div class="post-metadata">

**Author:** ![Bruce\_Gregory](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/4bbf92/32.png) [@Bruce\_Gregory](http://discourse.iapct.org/u/Bruce_Gregory)\
**Post date:** [December 20, 2000, 4:16pm UTC](http://discourse.iapct.org/t/evolution/13742/8 "2000-12-20T16:16:55Z")

</div>

{from Bruce Gregory (2000.1220.1116)]

> [From Chris Cherpas (2000.12.20.0740 PT)
> 
> I think selection is almost certainly involved. I don't know  
> of genetic mutations that accumulate in a particular direction  
> (e.g., bigger brain) without differential reproduction.

It's called genetic drift.

> Does "no selection pressure" mean that there's never been a  
> reproductive advantage in humans having a bigger brain?  
> OK, if no selection were involved, then a bigger brain would  
> have not improved the chances of reproducing more; but I would  
> think that the individuals who kept the smaller brain would  
> have a reproductive advantage because of less overhead...
> 
> Our big brain is a resource hog, using disproportionate  
> amounts of oxygen, blood, and glucose (i.e., considering  
> the amount of total body weight it takes). Also, the big  
> brain has been one reason why babies and mothers have died  
> during labor. This seems like a lot of trouble for something  
> that's reproductively neutral.

From a adaptationist perspective that's no doubt true. See \_The Spandrels  
of San Marcos\_ for an alternative perspective. I know of no evidence to  
refute the idea that if a phenotypic change is not disastrous, it may well  
prevail even if it does not confer reproductive advantage. The problem with  
the adaptationist approach is that it is immune to refutation. Sexual  
selection is the ultimate gotcha. It doesn't contribute to survival? Then  
it must be the result of sexual selection.

BG

> **···**
>
> > Best regards,  
> > cc

---

<div class="post-metadata">

**Author:** ![Isaac\_Kurtzer1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/i/439d5e/32.png) [@Isaac\_Kurtzer1](http://discourse.iapct.org/u/Isaac_Kurtzer1)\
**Post date:** [December 20, 2000, 4:20pm UTC](http://discourse.iapct.org/t/evolution/13742/9 "2000-12-20T16:20:53Z")

</div>

i.kurtzer (2000.1220.1015)

> [From Bruce Gregory (2000.1220.0735)]
> 
> \> Chris Cherpas (2000.12.20.0330 PT)  
> \>  
> \> I appreciate any/all of the recent posts about evolution  
> \> that were intended to illuminate. There are two, related,  
> \> points that I think are relevant to PCT:  
> \>  
> \> 1) The size of the brain in the lineage leading to humans appears  
> \> to have tripled between 2 million and 100,000 years ago.  
> \>  
> \> Would we expect that successive layers were added  
> \> corresponding to those theorized in HPCT, e.g., programs  
> \> followed by principles, followed by system concepts?
> 
> You are assuming that the levels in PCT are reflected by "layers" in the  
> brain. I know of no evidence to support this conjecture.

The derth of evidence is possibly a result of not clearly defining a  
hierarchical structure for \_functions\_ and an overemphasis on localizability  
of function. Further, a continuing argument has been betweeen hiercharchy  
vs loops, which is less a contrast than the meat and potatoes of HPCT.  
Although the anatomy still being worked out t is very clear that many  
regions are interconnected in nested feedback loops; for example, there are  
nested loops moving from brainstem nuclei forward through thalamus to  
primary sensory cortex then motor cortex back through to both (inner)  
thalamus and brainstem (outer). And thats the first 5-6 synapses. The  
cortical-basal ganglia and cortico-cerebellar connnections are all both  
reciprocal and significant; and these systems are again connected to the  
brainstem nuclei and to spinal nuclei. However, the enormous number of  
detail and a basic idea of what these nested loops do still needs to be  
worked out. This is actually open to many of you out there. If you have  
access to a good university then you can read up on the anatomy of a  
particular bit of jelly and develop hypotheses. Hint-hint. Warning, the  
simple diagrams will rapidly give way to a staggering complexity but there  
are some good intro's. I suggest Gordon Shepard's "Synaptic Organization of  
the Brain".  
Lastly, on evolution, there is some evidence of layered evolution via  
duplication and rearrangement of function. Schematically, A synapses to B;  
later B splits into B1 and B2 and A synapes to both; later still A synapses  
primarily to B1 while B2 is driven primarily by B1; similarly, B2 then  
feedbacks to B1 and A, and B1 to A). This can be seen in the SII, or  
somatosensensory cortex II, where it receives inputs in parallel with SI in  
cats and from SI in monkeys.

i.

---

<div class="post-metadata">

**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 20, 2000, 4:24pm UTC](http://discourse.iapct.org/t/evolution/13742/10 "2000-12-20T16:24:47Z")

</div>

[From Chris Cherpas (2000.12.20.0820 PT)]

Bruce Nevin (2000.12.20 10:56 EST)--

> ...When a female of another type of simian  
> comes into estrus (heat), there is a general free-for-all of competition  
> among the males, with a dominance hierarchy, sneaky hanky panky with  
> outlier adolescents, and so on, all well demonstrated. Then when estrus  
> ends and the sexy juices stop flowing it all stops. She is no longer  
> sexually attractive. With humans, there are two crucial differences. One,  
> women are attractive to men largely irrespective of their hormonal cycle;

This would seem to relate to the fact that ovulation in humans  
is invisible to would-be mates.

> and two, women are \*selectively\* attractive to \*particular\* men. To a  
> surprising degree (getting past rhetoric and hyped norms), what is a  
> turn-on for one is a pass for another. How did we get there, and why?

Ergo, sexual preferences for corresponding traits in potential mates.

> A monkey can only groom one other monkey at a time, but an individual who  
> can comment on other individuals in some way can maintain relationships  
> with 4 or 5 other individuals witnessing the commentary. Here comes your  
> topic of mimickry for starters, Chris. The earliest form of gossip probably  
> was nonverbal parody, I should think, such as has been observed among these  
> animals. (You'll have to look into the literature for yourself, it is quite  
> extensive I believe.) With more alliances, you can support a larger group  
> size; and with a larger groups surviving better than smaller groups,  
> individuals who can support more alliances through gossip survive better  
> than those who cannot.

I think that the gossip may provide even more basis for sexual  
selection, independent of survival advantages, too. Relatives  
of potential mothers, for example, might be influential in the  
choice of mates.

> Hope this helps.

How this relates to the evolution of HPCT functionality is what  
I'm ultimately shooting for, however speculatively, in this forum,  
so what you've said provides some of the pieces to my puzzle.

Best regards,  
cc

---

<div class="post-metadata">

**Author:** ![Bill\_Powers1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/8e7dd6/32.png) [@Bill\_Powers1](http://discourse.iapct.org/u/Bill_Powers1)\
**Post date:** [December 20, 2000, 4:52pm UTC](http://discourse.iapct.org/t/evolution/13742/11 "2000-12-20T16:52:09Z")

</div>

[From Bill Powers (2000.12.20.0945 MST)]

Chris Cherpas (2000.12.20.0330 PT)--

> &nbsp;&nbsp;&nbsp;Assuming a (roughly) serial evolution of successive HPCT layers  
> &nbsp;&nbsp;&nbsp;(i.e., the answer to question #1 above would be "yes"),  
> &nbsp;&nbsp;&nbsp;what mating preferences, and corresponding references in the  
> &nbsp;&nbsp;&nbsp;opposite sex for displaying what is preferred, would be missing  
> &nbsp;&nbsp;&nbsp;from the current human repertoire as one strips away layers  
> &nbsp;&nbsp;&nbsp;(i.e., system concepts, principles, programs...)?

Good approach. I'd prefer seeing it handled by comparative studies, because  
guessing about things that happened before recorded history can't really  
settle anything. In the animal kingdom there are doubtless organisms that  
have no system concepts, and other that lack principles \_and\_ system  
concepts, and so forth down to bacteria which may control nothing higher  
than sensations. Of course when such a study is actually undertaken, one of  
the first casualties might be my particular definitions of levels, but that  
wouldn't sadden me too much. A multidisciplinary cross-species  
investigation of hierarchical control would be a hell of an impressive  
undertaking.

It's hard for me to see how selective mating could produce a brain size  
larger than any that exist in a given population. Seems to me that mutation  
is also essential.

Best,

Bill P.

---

<div class="post-metadata">

**Author:** ![Bill\_Powers1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/8e7dd6/32.png) [@Bill\_Powers1](http://discourse.iapct.org/u/Bill_Powers1)\
**Post date:** [December 20, 2000, 4:59pm UTC](http://discourse.iapct.org/t/evolution/13742/12 "2000-12-20T16:59:07Z")

</div>

[From Bill Powers (2000.12.20.0955 MST)]

Bruce Gregory (2000.1220.0735)--

> You are assuming that the levels in PCT are reflected by "layers" in the  
> brain. I know of no evidence to support this conjecture.

You'll see some attempts at finding evidence in B:CP. I got a lot of my  
ideas about what levels might exist from studying some neuroanatomy and  
other readings, but my acquaintance with the literature of localization  
never was great. The most direct evidence is experiential and behavioral.

Best,

Bill P.

---

<div class="post-metadata">

**Author:** ![Bill\_Powers1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/8e7dd6/32.png) [@Bill\_Powers1](http://discourse.iapct.org/u/Bill_Powers1)\
**Post date:** [December 20, 2000, 5:08pm UTC](http://discourse.iapct.org/t/evolution/13742/13 "2000-12-20T17:08:10Z")

</div>

[From Bill Powers (2000.12.20.1006 MST)]

i.kurtzer (2000.1220.1015)--

> Lastly, on evolution, there is some evidence of layered evolution via  
> duplication and rearrangement of function. Schematically, A synapses to B;  
> later B splits into B1 and B2 and A synapes to both; later still A synapses  
> primarily to B1 while B2 is driven primarily by B1; similarly, B2 then  
> feedbacks to B1 and A, and B1 to A). This can be seen in the SII, or  
> somatosensensory cortex II, where it receives inputs in parallel with SI in  
> cats and from SI in monkeys.

Isaac, I am SO glad you are out there doing what you do.

Best,

bill P.

---

<div class="post-metadata">

**Author:** ![Bruce\_Gregory](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/4bbf92/32.png) [@Bruce\_Gregory](http://discourse.iapct.org/u/Bruce_Gregory)\
**Post date:** [December 20, 2000, 6:18pm UTC](http://discourse.iapct.org/t/evolution/13742/14 "2000-12-20T18:18:38Z")

</div>

[From Bruce Gregory (2000.1220.1318)]

> i.kurtzer (2000.1220.1015)
> 
> Lastly, on evolution, there is some evidence of layered evolution via  
> duplication and rearrangement of function. Schematically, A synapses to B;  
> later B splits into B1 and B2 and A synapes to both; later still A synapses  
> primarily to B1 while B2 is driven primarily by B1; similarly, B2 then  
> feedbacks to B1 and A, and B1 to A). This can be seen in the SII, or  
> somatosensensory cortex II, where it receives inputs in parallel with SI in  
> cats and from SI in monkeys.

I agree with your post up to this point. I don't understand the meaning of  
"layered evolution" in this (or any other!) context. What does duplication  
and rearrangement, for which we have evidence, have to do with "layered  
evolution"?

BG

---

<div class="post-metadata">

**Author:** ![Isaac\_Kurtzer1](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/i/439d5e/32.png) [@Isaac\_Kurtzer1](http://discourse.iapct.org/u/Isaac_Kurtzer1)\
**Post date:** [December 20, 2000, 6:43pm UTC](http://discourse.iapct.org/t/evolution/13742/15 "2000-12-20T18:43:58Z")

</div>

i.kurtzer

> [From Bruce Gregory (2000.1220.1318)]
> 
> \>i.kurtzer (2000.1220.1015)  
> \>  
> \>Lastly, on evolution, there is some evidence of layered evolution via  
> \>duplication and rearrangement of function. Schematically, A synapses to

B;

> \>later B splits into B1 and B2 and A synapes to both; later still A

synapses

> \>primarily to B1 while B2 is driven primarily by B1; similarly, B2 then  
> \>feedbacks to B1 and A, and B1 to A). This can be seen in the SII, or  
> \>somatosensensory cortex II, where it receives inputs in parallel with SI

in

> \>cats and from SI in monkeys.
> 
> I agree with your post up to this point. I don't understand the meaning of  
> "layered evolution" in this (or any other!) context. What does duplication  
> and rearrangement, for which we have evidence, have to do with "layered  
> evolution"?

The term "layered evolution" was a shorthand for the sucessive addition of a  
new level of control throughout the evolutionary record. Others have used  
even more high-falootin' phrases such as "metasystem transition" but the  
point is the same. I was describing a known instance in physiology where a  
higher level system is created by duplication and shuffling.

i.

---

<div class="post-metadata">

**Author:** ![Bruce\_Gregory](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/4bbf92/32.png) [@Bruce\_Gregory](http://discourse.iapct.org/u/Bruce_Gregory)\
**Post date:** [December 20, 2000, 6:49pm UTC](http://discourse.iapct.org/t/evolution/13742/16 "2000-12-20T18:49:41Z")

</div>

[From Bruce Gregory (2000.1220.1349)]

> i.kurtzer
> 
> The term "layered evolution" was a shorthand for the sucessive addition of a  
> new level of control throughout the evolutionary record. Others have used  
> even more high-falootin' phrases such as "metasystem transition" but the  
> point is the same. I was describing a known instance in physiology where a  
> higher level system is created by duplication and shuffling.

If I ever say "metasystem transition" I hope you'll wash out my mouth with  
soap...

BG

---

<div class="post-metadata">

**Author:** ![bnhpct](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bnhpct/32/34_2.png) [@bnhpct](http://discourse.iapct.org/u/bnhpct)\
**Post date:** [December 20, 2000, 6:53pm UTC](http://discourse.iapct.org/t/evolution/13742/17 "2000-12-20T18:53:48Z")

</div>

[From Bruce Nevin (2000.12.20 10:56 EST)]

Chris Cherpas (2000.12.20.0330 PT)--

> 2) The radical difference between the brains of humans and other  
> &nbsp;&nbsp;&nbsp;&nbsp;primates is generally easier to account for on the basis of selective  
> &nbsp;&nbsp;&nbsp;&nbsp;mating, rather than via physical or interspecies pressures -- if  
> &nbsp;&nbsp;&nbsp;&nbsp;you disagree, I'd be interested in knowing how/why.
> 
> &nbsp;&nbsp;&nbsp;&nbsp;Assuming a (roughly) serial evolution of successive HPCT layers  
> &nbsp;&nbsp;&nbsp;&nbsp;(i.e., the answer to question #1 above would be "yes"),  
> &nbsp;&nbsp;&nbsp;&nbsp;what mating preferences, and corresponding references in the  
> &nbsp;&nbsp;&nbsp;&nbsp;opposite sex for displaying what is preferred, would be missing  
> &nbsp;&nbsp;&nbsp;&nbsp;from the current human repertoire as one strips away layers  
> &nbsp;&nbsp;&nbsp;&nbsp;(i.e., system concepts, principles, programs...)?
> 
> &nbsp;&nbsp;&nbsp;&nbsp;A specific example I mentioned in a previous post was whether  
> &nbsp;&nbsp;&nbsp;&nbsp;imitating successful courting would be possible without the  
> &nbsp;&nbsp;&nbsp;&nbsp;system concept layer.

Dunbar and Lovelace (in the Johansen/Edey book about the hominid Lucy) both give very interesting accounts of the social factors favoring (and favored by) increased cognitive ability.

Animals may be compared as to their reproductive strategy. Oysters are very prolific of potential offspring but provide zero nurturance and protection. Apes, our ancestors, went to the other extreme. An ape mother must nurture her single baby 5 years or before she can have another baby. Whereas infants of other simians grasp the mother with hands, feet, and often tail, leaving the mother's hands free for climbing and foraging, apes must use one or both hands to hold the baby. Foraging was made more difficult because monkeys evolved a capacity to eat unripe fruit, whereas we apes like most critters cannot tolerate the tannins that make unripe fruit bitter and spoil our digestion. The branch that became the great apes and chimps moved deeper into the forest. The branch that became hominids (and the now extinct africanus and robustus lines) moved out into the open.

Lovelace makes a convincing argument that erect posture preceded this move. He does not connect it to competition with monkeys for food, as Dunbar does, but to the problem of procreation. Locomotion is a way out of the reproductive blind alley where the apes were (and are) trapped. The mother can stay close to a home base, where all the resources and sanctuaries are familiar and near. The male has hands free to bring her gifts. But more fundamental under this is sex. When a female of another type of simian comes into estrus (heat), there is a general free-for-all of competition among the males, with a dominance hierarchy, sneaky hanky panky with outlier adolescents, and so on, all well demonstrated. Then when estrus ends and the sexy juices stop flowing it all stops. She is no longer sexually attractive. With humans, there are two crucial differences. One, women are attractive to men largely irrespective of their hormonal cycle; and two, women are \*selectively\* attractive to \*particular\* men. To a surprising degree (getting past rhetoric and hyped norms), what is a turn-on for one is a pass for another. How did we get there, and why?

Skipping the marginal corollaries in related species, which Lovelace discusses, what this does is enhance the safety of the female staying near home base and helping mothers (or being helped by other females) with the care of infants. And what it does is support particular males developing references to provide food and other gifts to particular females and their offspring.

Back to Dunbar. In the open country, group size had to increase. Individuals physically on the margins of a group are most vulnerable to predators, and in a small group a higher percentage are on the margins. But group size is limited by the number of alliances that each individual can maintain. Dunbar has some numbers about monkey bands, human village size, and so on, and the numbers support his thesis quite well.

Simians (among others) maintain social groupings by grooming. Grooming is time intensive. An individual can maintain grooming relations with only a few others, and the rest of the time must be for foraging, sleep, escape, group movement, etc. These grooming relations establish and maintain alliances that have obvious benefit for survival and health of mothers and their offspring.

A monkey can only groom one other monkey at a time, but an individual who can comment on other individuals in some way can maintain relationships with 4 or 5 other individuals witnessing the commentary. Here comes your topic of mimickry for starters, Chris. The earliest form of gossip probably was nonverbal parody, I should think, such as has been observed among these animals. (You'll have to look into the literature for yourself, it is quite extensive I believe.) With more alliances, you can support a larger group size; and with a larger groups surviving better than smaller groups, individuals who can support more alliances through gossip survive better than those who cannot.

With the linear growth of allies, you have an exponential growth of relationships to keep track of -- not only me to her, but her to my other allies and her to "our" adversaries. This demands (and is supported by) greater cognitive capacity. With this greater cognitive capacity comes the possibility of more sophisticated gossip, the refinement of animal cries (already denotative) to words, the institutionalizing of word-groupings that circumstantially go together into particular preferred sequences, the institutionalizing of particular ways of sequencing words analogically extended to other words in novel sequences giving rise to syntax and the origins of language, all of which requires (and is supported by) increase in brain size. Which is possible only by extending the infant's time in utero and with an extended period of dependency (childhood), and is possible only in context of a protected home base for mothers and infants, social cooperation, etc.

That's a quick Cook's Tour. Those two books should give you plenty to chew on. I am sure that Lieberman's book is very worthwhile, but haven't read it, and the other titles I mentioned, and beyond that the literature of primate studies is quite large, not to mention other social critters, like that remarkable work on Grey Parrots.

Hope this helps.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Be well,

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Bruce Nevin

> **···**
>
> At 03:34 AM 12/20/2000 -0800, Chris Cherpas wrote:

---

<div class="post-metadata">

**Author:** ![bnhpct](http://discourse.iapct.org/user_avatar/discourse.iapct.org/bnhpct/32/34_2.png) [@bnhpct](http://discourse.iapct.org/u/bnhpct)\
**Post date:** [December 20, 2000, 10:16pm UTC](http://discourse.iapct.org/t/evolution/13742/18 "2000-12-20T22:16:50Z")

</div>

[From Bruce Nevin (2000.12.20 14:15 ET)]

Chris Cherpas (2000.12.20.0740 PT)

> **···**
>
> At 07:56 AM 12/20/2000 -0800, Chris Cherpas wrote:
> 
> > Our big brain is a resource hog, using disproportionate  
> > amounts of oxygen, blood, and glucose (i.e., considering  
> > the amount of total body weight it takes). Also, the big  
> > brain has been one reason why babies and mothers have died  
> > during labor. This seems like a lot of trouble for something  
> > that's reproductively neutral.
> 
> Big brain and upright posture -- most obviously the latter, certainly because of childbirth/childhood consequences the former -- make no evolutionary sense without reproductive advantage. Read Lovelace and Dunbar.
> 
> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Bruce Nevin

---

<div class="post-metadata">

**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 21, 2000, 12:05am UTC](http://discourse.iapct.org/t/evolution/13742/19 "2000-12-21T00:05:21Z")

</div>

[From Chris Cherpas (2000.12.20.1600 PT)]

Bill Powers (2000.12.20.0945 MST)--

> It's hard for me to see how selective mating could produce  
> a brain size larger than any that exist in a given population.  
> Seems to me that mutation is also essential.

I wasn't explicit about the sources of variation upon which  
selective mating would operate. If the species were totally  
monogomous and mated assortively (i.e., top guy mates with  
top gal, 2nd bananas pair up, and so forth), then those at  
the bottom of the barrel would presumably have offspring  
that were much less viable, given that selective mating is  
based to any extent on fitness indicators. That would move  
the average for mate preferences and traits preferred, but  
without a source of variation other than recombination,  
there would be no reason to expect brain sizes much larger  
than the largest in the starter population. With polygyny,  
the process would move faster (the rich get richer and the  
poor get poorer model), but without another source of  
variation, there would be no obvious way to get a larger  
largest brain.

So, yes, I'm assuming mutation (and I generally do when  
considering evolution). The more genes needed to produce  
a structure, the more chances there are for mutations to  
screw it up. So, mating preferences based on complex (multi-gene)  
phenotypes (like more powerful brains) would be even more indicative  
of fitness than simpler reproductive advertisements, like  
florescent genitals.

Best regards,  
cc

---

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**Author:** ![Chris\_Cherpas](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/c/a3d4f5/32.png) [@Chris\_Cherpas](http://discourse.iapct.org/u/Chris_Cherpas)\
**Post date:** [December 21, 2000, 12:43am UTC](http://discourse.iapct.org/t/evolution/13742/20 "2000-12-21T00:43:52Z")

</div>

[From Chris Cherpas (2000.12.1630 PT)]

Chris Cherpas (2000.12.20.0740 PT)--

> > I think selection is almost certainly involved. I don't know  
> > of genetic mutations that accumulate in a particular direction  
> > (e.g., bigger brain) without differential reproduction.

Bruce Gregory (2000.1220.1116)--

> It's called genetic drift.

I agree that you can get accumulated changes via genetic  
drift (without selection) but, then, I don't think of drift as  
involving mutation, but rather as the outcome of recombination.  
A genetic drift account of big-brained humans would be favored  
if our proto-humans were a small population that essentially  
lost its "smaller brain size" alleles and just fixed on the  
"biggest brain size" allele, out of the starter sample set.  
That situation would also result in little likelihood of  
any further changes (e.g., via selection) since there'd be  
no variation left from which to select.

Bruce Gregory (2000.1220.1116)--

> See \_The Spandrels of San Marcos\_ for an alternative perspective.

Good reference. A finch in the hand is worth two in the imagination.

Bruce Gregory (2000.1220.1116)--

> The problem with the adaptationist approach is that it is immune  
> to refutation. Sexual selection is the ultimate gotcha. It doesn't  
> contribute to survival? Then it must be the result of sexual selection.

I agree in principle, and didn't mean to [over]state my proposal so  
as to assume a pure adaptionist approach -- i.e., one that would preclude  
other possibilities. Nor have I seen an argument that makes selective  
mating an impossibility.

Best regards,  
cc

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