Current Problems form another Evolutionary Prediction

[Tenspace]

This one hit me like a lead brick last night. Let me bring it up here, see if anyone else agrees.

Evolution predicts the current crisis state of our physical condition in the human population, primarily in the U.S.

Before we became organized and agrarian, the small tribes of humans that dotted this planet faced much harsher selection pressures. I guess you could call it caveman economics - if the tribe's member could not contribute to the tribe, then they were most likely left behind for the predators to take care of. I just cannot see early man lugging Grandma along while tracking game or avoiding the cold. I also cannot see them caring for a deformed baby. I'm guessing any gross deformities were left behind as well.

What a mean but honest method of avoiding deleterious baggage in the tribe.

The part that provided the virtual smack upside the head is this: many 'conditions' we deal with today are relatively recent. Most serious physical ailments affect children and post-breeders. And, conditions like obesity, manic depression, bipolar, OCD would not flourish in early man's environment, because of the negative effect on the tribe.

Evolutionary theory should predict these very things - if you no longer remove your problems when they occur, then you're left with a population diluted by propensities for gluttony, inability to associate with the local population, and of course the obvious ones, like Down's Syndrome, Cushing's, Tay-Sachs, etc etc etc.

So, what do you guys think? Squid, I'm sure this has been written about - have you any references for me? :)

We were actually discussing something very similar in another thread Ten. It is an interesting point - once I finally realized what was being discussed (which usually the most often reason for continuing arguments - the argumentors are on different pages). However, this isn't really a specific item I'm familiar with.

It is interesting to want to know what may come of this course - like I said in the other thread, someone had said to me we'd be a populace of idiots ruled by the intelligent few - referring to the fact that lack of education and low SES correlates with a much higher birth rate and the whole situation is self perpetuating for many reasons.

Here's the thread where me, whoneedscience, and rocketman discuss the issue:

http://ravingatheist.com/forum/viewt...hp?id=3433&p=4

At first I thought the idea was that because of cultural intervention, biological evolution ceases all together but I wasn't clear on what the proposal was but we got it cleared up.

Never the less, I shall see if I happen to run across anything about it in the literature.

Actually--there is strong evidence that Neandethals --at least cared very much for the aged and deformed offspring of their tribes. THe caves at shanidar demonstrate the presence of disabled individuals who would ahve needed long term and intensive care to survive.

You are correct in assuming that the problems of an Age of Food--(my term) provide diseases of excess.

I'm a victim myself--type two diabetes due to weight and a family genetic propensity.

however, culture is not mandated by the reproductive success of the individual species members. If we were to be thrown back into the survival situation you speak of--then these diseases would almost certainly be a selection pressure again.

Presently though--the guy in the wheel chair has the potential to treat disease absent any need for an athletes body.

The airplane designer doesn't need to be absent sickle cell anemia.

Maybe the girl with cystic fibrosis is the one who figures out the mechanics to prevent the asteroid from hitting.

Or cures the next great pandemic. Or is the sister of the guy that does who provides him with the support through his own dark times to enable him to get there...

Yes-these diseases are limiting--but in terms of culture--they do not prevent the additon of new ideas, new configurations of ideas and support for those who produce to have an impact.

It's a race really--see if we can solve the problem before we evolve to a state of total incusion-survivability of what once killed us, without utterly destroying the capacity of our environment to sustain us.

I think it's exciting and a worthy goal.

Tenspace wrote

Before we became organized and agrarian, the small tribes of humans that dotted this planet faced much harsher selection pressures. I guess you could call it caveman economics - if the tribe's member could not contribute to the tribe, then they were most likely left behind for the predators to take care of. I just cannot see early man lugging Grandma along while tracking game or avoiding the cold. I also cannot see them caring for a deformed baby. I'm guessing any gross deformities were left behind as well.

What a mean but honest method of avoiding deleterious baggage in the tribe.

This was probably true for very early apes, but I think you're drawing the line a bit late. Once humans banded together into hunter-gatherer societies, there would have been a huge demand for Grandma. She may not be able to move particularly quickly, but neither can healthy children, so when the strong hunters go off to get food, Grandma would have been the ideal babysitter. As an added bonus, you also have a (more than not) reliable source of information about herd movements, weather conditions, etc. as well as someone to educate your kids. In other words, cultural evolution is kicked into high gear.

As for deformed babies, yeah, they probably would have tied them to a tree for the demons, but rocketman makes a good argument for why this is a bad thing in the other thread.

Tenspace wrote

The part that provided the virtual smack upside the head is this: many 'conditions' we deal with today are relatively recent. Most serious physical ailments affect children and post-breeders. And, conditions like obesity, manic depression, bipolar, OCD would not flourish in early man's environment, because of the negative effect on the tribe.

Evolutionary theory should predict these very things - if you no longer remove your problems when they occur, then you're left with a population diluted by propensities for gluttony, inability to associate with the local population, and of course the obvious ones, like Down's Syndrome, Cushing's, Tay-Sachs, etc etc etc.

This does seem to be a common conception (or perhaps misconception) among many people, especially theists who see evolution as promoting evil. I just don't see it that way. For one, Down Syndrome is not genetic, it's caused by a failure in the chromosomes to separate, I believe, and it's linked to women having children late in life. Many other diseases (Tay-Sachs might be one of them) stil exist because the carriers often survive to reproduce, and then die shortly after (which actually may help to spread the allele, because they aren't competing with their children. Is this the result of humans living longer? Yeah, but that doesn't mean they weren't around before. We just didn't encounter them on the same level.

I've also read many articles (sorry, no link, I'm really supposed to be doing other work right now, so feel free to tear me a new one, squid/rocketman) suggesting that conditions like OCD and ADD were even selected for in our early society. Early man would probably not have cared if they had serious mental health issues, so long as they could benefit themselves and others in specific ways (the key is that society allows for specialization, which is the very definition of many such "disorders"). OCD may be a terrible disorder by today's standards, but maybe it helped cavemen tend fire better bacause one member of their tribe was obsessed with gathering wood, or maybe it helped them keep diseased rats out of their cave. The argument I've heard for ADD is that it would have made for more charismatic leaders. Sure, some tribes might have gotten themselves killed when their hyperactive chief led them in a suicide charge against a smilodon, but you have to also consider how many tribes died out because they had no one to lead them on any hunt. This, in itself, could answer the question of how depression established itself in the gene pool. You want your tribe to go on a crazy charge sometimes, but most of the time humans actually were best off sitting around doing nothing. Even today, most so-called primitive tribes spend most of their time at leisure. Depression is only a disorder in terms of modern society, where people are expected to be stressed out all the time.

[Tenspace]

whoneedscience wrote

This was probably true for very early apes, but I think you're drawing the line a bit late. Once humans banded together into hunter-gatherer societies, there would have been a huge demand for Grandma. She may not be able to move particularly quickly, but neither can healthy children, so when the strong hunters go off to get food, Grandma would have been the ideal babysitter. As an added bonus, you also have a (more than not) reliable source of information about herd movements, weather conditions, etc. as well as someone to educate your kids. In other words, cultural evolution is kicked into high gear.


As for deformed babies, yeah, they probably would have tied them to a tree for the demons, but rocketman makes a good argument for why this is a bad thing in the other thread.

I'm referring to when grandma is no longer able to care for the children. What's wrong with leaving her parked under her a distant tree, comfortable, tears in the eyes, kisses on the forehead. The predators would finish things up. I know, as well, that the burial rites were probably predator and contagion avoidance methods. But again, I just can't see a nomadic tribe dragging along the alzheimer's-affected and flipper babies because of familial love or tribal altruism.

WNS wrote

This does seem to be a common conception (or perhaps misconception) among many people, especially theists who see evolution as promoting evil. I just don't see it that way. For one, Down Syndrome is not genetic, it's caused by a failure in the chromosomes to separate, I believe, and it's linked to women having children late in life. Many other diseases (Tay-Sachs might be one of them) stil exist because the carriers often survive to reproduce, and then die shortly after (which actually may help to spread the allele, because they aren't competing with their children. Is this the result of humans living longer? Yeah, but that doesn't mean they weren't around before. We just didn't encounter them on the same level.

You're right on Down's... Aneuploidy appears to be spontaneous, not counting for any environmental triggers that may increase susceptibility among certain populations. But that's the exception, rather than the rule, I would think. Again, I'm looking for a predictive explanation, not a foundation for 21st century eugenics.

I've also read many articles (sorry, no link, I'm really supposed to be doing other work right now, so feel free to tear me a new one, squid/rocketman) suggesting that conditions like OCD and ADD were even selected for in our early society. Early man would probably not have cared if they had serious mental health issues, so long as they could benefit themselves and others in specific ways (the key is that society allows for specialization, which is the very definition of many such "disorders"). OCD may be a terrible disorder by today's standards, but maybe it helped cavemen tend fire better bacause one member of their tribe was obsessed with gathering wood, or maybe it helped them keep diseased rats out of their cave. The argument I've heard for ADD is that it would have made for more charismatic leaders. Sure, some tribes might have gotten themselves killed when their hyperactive chief led them in a suicide charge against a smilodon, but you have to also consider how many tribes died out because they had no one to lead them on any hunt. This, in itself, could answer the question of how depression established itself in the gene pool. You want your tribe to go on a crazy charge sometimes, but most of the time humans actually were best off sitting around doing nothing. Even today, most so-called primitive tribes spend most of their time at leisure. Depression is only a disorder in terms of modern society, where people are expected to be stressed out all the time.

Those are great points - I think the more obvious conditions would be selected against - OCD has potential positive benefits, but Tourette's? Severe Autism? I'm guessing these may be more recent anomalies.

The most common item I've ran across is the allegation that human evolution has stopped all together, which is silly. However the idea of our culture changing the idea of what is advantageous and incurs "fitness" is another story. Obviously if you are say, physically handicapped you will have a hard time even in our modern society - BUT, it won't keep you from reproducing.

Once horrible diseases that would have killed off someone in childhood or adolesence now can be managed until old age - these genes still will propogate through our gene pool over generations. Natural selection hasn't stopped...but the parameters have changed. Here's what a snippet from Talk Origins says on the evolution stopping issue:

1. There is evidence that humans have evolved in the last several thousand years and continue to evolve.

* Analysis of variation in the human genome indicates that genes associated with brain size have evolved over approximately the last 37,000 years and 5800 years (Evans et al. 2005; Mekel-Bobrov et al. 2005).
* Sickle-cell resistance has evolved to be more prevalent in areas where malaria is more common.
* Lactose tolerance has evolved in conjunction with cultural changes in dairy consumption (Durham 1992).
* Some humans have recently acquired mutations which confer resistance to AIDS (Dean et al. 1996; Sullivan et al. 2001) and to heart disease (Long 1994; Weisgraber et al. 1983).

References:

1. Dean, M. et al. 1996. Genetic restriction of HIV-1 infection and progression to AIDS by a deletion allele of the CKR5 structural gene. Science 273: 1856-1862.
2. Durham, William H. 1992. Coevolution: Genes, Culture, and Human Diversity. Stanford, CA: Stanford University Press.
3. Evans, Patrick D. et al. 2005. Microcephalin, a gene regulating brain size, continues to evolve adaptively in humans. Science 309: 1717-1720.
4. Long, Patricia. 1994. A town with a golden gene. Health 8(1) (Jan/Feb.): 60-66.
5. Mekel-Bobrov, Nitzan et al. 2005. Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens. Science 309: 1720-1722.
6. Sullivan, Amy D., Janis Wigginton and Denise Kirschner. 2001. The coreceptor mutation CCR5-delta-32 influences the dynamics of HIV epidemics and is selected for by HIV. Proceedings of the National Academy of Science USA 98: 10214-10219.
7. Weisgraber K. H., S. C. Rall Jr., T. P. Bersot, R. W. Mahley, G. Franceschini, and C. R. Sirtori. 1983. Apolipoprotein A-I Milano. Detection of normal A-I in affected subjects and evidence for a cysteine for arginine substitution in the variant A-I. Journal of Biological Chemistry 258: 2508-2513.

Source - http://www.talkorigins.org/indexcc/CB/CB928_2.html

A news article in New Scientist talks about a study which touches close to the topic, although it is not specifically dealing with how current situations will change our population:

Moyzis speculates that we may have similarly “domesticated” ourselves with the emergence of modern civilisation.

“One of the major things that has happened in the last 50,000 years is the development of culture,” he says. “By so radically and rapidly changing our environment through our culture, we’ve put new kinds of selection [pressures] on ourselves.”

Genes that aid protein metabolism – perhaps related to a change in diet with the dawn of agriculture – turn up unusually often in Moyzis’s list of recently selected genes. So do genes involved in resisting infections, which would be important in a species settling into more densely populated villages where diseases would spread more easily. Other selected genes include those involved in brain function, which could be important in the development of culture.

But the details of any such sweeping survey of the genome should be treated with caution, geneticists warn. Now that Moyzis has made a start on studying how the influence of modern human culture is written in our genes, other teams can see if similar results are produced by other analytical techniques, such as comparing human and chimp genomes.

Source - http://www.newscientist.com/article.ns?id=dn8483

The abstract from the paper itself can be fairly confusing:

By using the 1.6 million single-nucleotide polymorphism (SNP) genotype data set from Perlegen Sciences [Hinds, D. A., Stuve, L. L., Nilsen, G. B., Halperin, E., Eskin, E., Ballinger, D. G., Frazer, K. A. & Cox, D. R. (2005) Science 307, 1072-1079], a probabilistic search for the landscape exhibited by positive Darwinian selection was conducted. By sorting each high-frequency allele by homozygosity, we search for the expected decay of adjacent SNP linkage disequilibrium (LD) at recently selected alleles, eliminating the need for inferring haplotype. We designate this approach the LD decay (LDD) test. By these criteria, 1.6% of Perlegen SNPs were found to exhibit the genetic architecture of selection. These results were confirmed on an independently generated data set of 1.0 million SNP genotypes (International Human Haplotype Map Phase I freeze). Simulation studies indicate that the LDD test, at the megabase scale used, effectively distinguishes selection from other causes of extensive LD, such as inversions, population bottlenecks, and admixture. The {approx}1,800 genes identified by the LDD test were clustered according to Gene Ontology (GO) categories. Based on overrepresentation analysis, several predominant biological themes are common in these selected alleles, including host-pathogen interactions, reproduction, DNA metabolism/cell cycle, protein metabolism, and neuronal function.

Source - Wang, E., Kodama, G., Baldi, P., & Moyzis, R. (2006). Global landscape of recent inferred Darwinian selection for Homo sapiens. PNAS, 103, 135-140.

Also there is evidence of recent evolution in teeth:

Even within the last 100,000 years, the long-term trends towards smaller molars and decreased robustness can be discerned. The face, jaw and teeth of Mesolithic humans (about 10,000 years ago) are about 10% more robust than ours. Upper Paleolithic humans (about 30,000 years ago) are about 20 to 30% more robust than the modern condition in Europe and Asia. These are considered modern humans, although they are sometimes termed "primitive". Interestingly, some modern humans (aboriginal Australians) have tooth sizes more typical of archaic sapiens. The smallest tooth sizes are found in those areas where food-processing techniques have been used for the longest time. This is a probable example of natural selection which has occurred within the last 10,000 years (Brace 1983).

Source - http://www.talkorigins.org/faqs/homs/species.html

And the Brace (1983) referecence:

Brace C.L. (1983): Humans in time and space. In L.R. Godfrey (Ed.), Scientists confront creationism. (pp. 245-82). Toronto: George J. McLeod.

However, this doesn't do much to address our point in question. The closest thing I could find to answer some of these questions was something called biocultural anthropology:

Recently however some anthropologists have become interested in the effects of culture -- especially the effects of technologically advanced modern culture -- on the built-in biological capacities and limitations of humankind. They have stimulated an resurgence of interest in some questions that have been around for a long time. How, for example, has the extraordinary growth in the content of the cultural environment over the past few thousand years affected the course of human biological evolution? What might be reasonably inferred about our species future from such rampaging cultural growth? What does an organism hardwired to adjust to a cultural environment that elevates within group competition over cooperation? How does the widespread acceptance of a belief in the primacy of adult gratification affect the biological well being of children? What biological effects do non-governmental service organizations have when they seek to reduce the rate population growth, to ameliorate malnutrition, to increase life expectancy, or to reduce infant deaths? In what, if any, ways are human beings affected by the persistence of beliefs and institutions formed out of cultural conditions that passed out of existence long ago? Has the accelerating rate of growth in the contents of the cultural environment become more formidable than the natural environment as a challenge to the continued survival of humankind? How do cultural processes that degrade the natural environment affect human biological potential? How do the cultural processes which concentrate wealth in the hands of a few affect the biological capacities of the many?

These represent a small sample of the questions that biocultural anthropology could ask. Each of these, for example, could be partitioned further into questions concerning the effects of culture upon biologically defined subcategories such as sex, race and age differences. There seems to be plenty of work to be done

The questions of importance to biocultural anthropology strike at the heart of some of the most pressing issues that confront our species, us and every one else, right here and right now. What follows here is a proposal which seeks to lay a foundation upon which the work could proceed.

Source - http://spot.colorado.edu/~kelso/Biologicalanth.html

There are some studies in the anthropology sector that insinuate that culture has greatly impacted our evolution:

"Modern" human form results from reduction in both craniofacial and postcranial Middle Pleistocene levels of robustness. In a classic manifestation of mosaic evolution, these reductions began at different times and proceeded at different rates in different places. They were produced by mutations acting alone when particular cultural developments eased the forces of selection. The separate regional appearances of obligatory cooking and projectile use late in the Middle Pleistocene produced separate and predictable manifestations of morphological reduction. There is no common "modern" configuration, and no single geographic locale was responsible for the various aspects of reduction that contribute to "modern" morphology.

Source - Brace, C. L. (1995). Biocultural Interaction and the Mechanism of Mosaic Evolution in the Emergence of "Modern" Morphology. American Anthropologist, 97, 711-721.

But, I haven't delved much into the issue. It would be an interesting item to research though. Very interesting. Let me know if you run across anything salient in any searches on the subject.

[Tenspace]

Dude, you are the reference God. I may even consider adapting the cephalopod as my deity to honor the knowledge of these deepwater geniuses. :)

May the tentacles of knowledge embrace your brain.

:D

Hehe, no problemo my friend.

[Philboid Studge]

One thing that I always suspected was true but never saw in print until recently is that the part of the brain that processes (creates?) emotions -- the prefrontal cortex -- evolved most recently. I suppose this was concurrent with Homo becoming a cooperator, in which things like face-recognition, empathy, etc emerged as survival strategies. Caring for granny and the disabled is probably a consequence of that -- and perhaps an ironic one, since expending resources on non-childbearing, unproductive clan members seems contrary to maximizing survival.

Tenspace, isn't this a rather loose usage of the word 'prediction'? Or is there a legitimate scientific usage in which a prediction can be 'formed' retroactively through observation of present conditions?

The prefrontal cortex wouldn't be the "creator" of emotions, that distinction would go to the limbic system. However, the prefrontal does take part in the process. It works as the executive - providing inhibition or lack thereof.

Some information on the prefrontal cortex:

The prefrontal association cortex is important for cognitive functions and for organizing behavior, including the memories and motor plans that are necessary for interacting with our environment. For example, patients with damage to the prefrontal cortex blindly repeat motor acts irrespective of their efficacy (75).

Source - Martin, J. (1996). Neuroanatomy. (6th ed.). Stamford: Appleton & Lange

The most anterior portion of the frontal lobe, the prefrontal cortex, forms a large proportion of the brain in species with large overall brain but only a small portion if the species has a small brain. For example, it is large in humans and all the great apes. It is not the primary target of any single sensory system, but it receives information from all of them, each projecting to different parts of the prefrontal cortex. Neurons of the prefrontal cortex have largre dendrites covered with more dendritic spines than dendrites in other cortical areas. Prefrontal neurons have up to 16 times as many dendritic spines as neurons in the primary visual cortex in the occipital lobe. The result is that the prefrontal cortex can integrate an enormous amount of information (97).

People with prefrontal damage lose their inhibitions, ignoring the rules of polite, civilized conduct. They often act impulsively because they fail to calculate adequately the probable outcomes of their behaviors (99).

Source - Kalat, J. (2004). Biological Psychology. (8th ed.). Belmont: Wadsworth/Thomson Learning.

The parts of teh frontal lobe anterior to areas 4 and 6 do not cause movements when stimulated and are called prefrontal cortex. This part of the brain expanded dramatically during mammalian evolution and now occupies the inside of the distinctive high forehead of humans (527).

Source - Nolte, J. (1993). The Human Brain. (4th ed.). St. Louis: Mosby.

You are correc though that the extremely "developed" prefrontal cortex in humans is a late comer evolutionarily. It is the captain of the ship we call our brain.

Interestingly it is the last major part of the cortex to fully develop - at approximately 18 - 21 for girls and 20 - 23 for guys on average. This information that came to light has had some implications especially for juvenile crime and debate still rages especially when adolescents are tried as adults.

From the PBS website about the Frontline special on the brain:

The prefrontal cortex sits just behind the forehead. It is particularly interesting to scientists because it acts as the CEO of the brain, controlling planning, working memory, organization, and modulating mood. As the prefrontal cortex matures, teenagers can reason better, develop more control over impulses and make judgments better. In fact, this part of the brain has been dubbed "the area of sober second thought."

The fact that this area was still growing surprised the scientists. Although they knew that the brain of a baby grew by over-producing synapses, or connections, they had not known that there was a second period of over-production. In a baby, the brain over-produces brain cells (neurons) and connections between brain cells (synapses) and then starts pruning them back around the age of three. The process is much like the pruning of a tree. By cutting back weak branches, others flourish. The second wave of synapse formation described by Giedd showed a spurt of growth in the frontal cortex just before puberty (age 11 in girls, 12 in boys) and then a pruning back in adolescence.

Even though it may seem that having a lot of synapses is a particularly good thing, the brain actually consolidates learning by pruning away synapses and wrapping white matter (myelin) around other connections to stabilize and strengthen them. The period of pruning, in which the brain actually loses gray matter, is as important for brain development as is the period of growth. For instance, even though the brain of a teenager between 13 and 18 is maturing, they are losing 1 percent of their gray matter every year.

Giedd hypothesizes that the growth in gray matter followed by the pruning of connections is a particularly important stage of brain development in which what teens do or do not do can affect them for the rest of their lives. He calls this the "use it or lose it principle," and tells FRONTLINE, "If a teen is doing music or sports or academics, those are the cells and connections that will be hardwired. If they're lying on the couch or playing video games or MTV, those are the cells and connections that are going to survive."

Source - http://www.pbs.org/wgbh/pages/frontl...dolescent.html

I would have to agree that the evolution of the prefrontal cortex can be implicated as contributing much to the production of our social tendencies.

[Victus]

Alot of psychological disorders are becoming more prevalent as the world 'shrinks'. Some believe this is because of an actual change in the population, others the sinple fact that we are becoming better at detecting them (I would propose that the truth lies somewhere in between the two).

One that I find the most interesting is psychopathy (most interesting disorder I've ever seen). Several researchers have deemed psychopaths to be 'interspecies predators'. It's like their built for playing the social game like a fiddle. They have deficiencies in their amigdyla (spelled so so wrong) which can cause a sense of fearlessness. Furthermore they have deficits in their prefrontal cortexes, which has been linked to pathological lying, conning, manipulative behaviors and the like. Also, where intelligence usually inhibits criminal behaviors, in psychopaths it actually seems to make them 'better' criminals.

Some researchers in psychopathy believe that it is a fairly recent evolutionary development (heredity research pending) which allows a limited number of 'wolves' to exist inside of a herd of 'sheep'.

Anyone else have opinions on this interesting disorder?

PS: Too lazy to cite my sources.. they're on the table next to me

[Philboid Studge]

solidsquid wrote

The prefrontal cortex wouldn't be the "creator" of emotions, that distinction would go to the limbic system. However, the prefrontal does take part in the process. It works as the executive - providing inhibition or lack thereof.

Got it, thanks. (And I see you further explicate thus over at the Brain Awareness thread as well.) :)

[a different tim]

http://www.newscientist.com/channel/...mg18925421.300

If anyone's a subscriber.....

[Philboid Studge]

ADT, I thought you were a subscriber? (from ProveIt's thread on 'Magazines') I posted that same link on another of the many evo threads floating around, but no one seems to have full access.

[HeathenLifer]

Rocketman wrote

Actually--there is strong evidence that Neandethals --at least cared very much for the aged and deformed offspring of their tribes. THe caves at shanidar demonstrate the presence of disabled individuals who would ahve needed long term and intensive care to survive.

You are correct in assuming that the problems of an Age of Food--(my term) provide diseases of excess.

I'm a victim myself--type two diabetes due to weight and a family genetic propensity.

however, culture is not mandated by the reproductive success of the individual species members. If we were to be thrown back into the survival situation you speak of--then these diseases would almost certainly be a selection pressure again.

Presently though--the guy in the wheel chair has the potential to treat disease absent any need for an athletes body.

The airplane designer doesn't need to be absent sickle cell anemia.

Maybe the girl with cystic fibrosis is the one who figures out the mechanics to prevent the asteroid from hitting.

Or cures the next great pandemic. Or is the sister of the guy that does who provides him with the support through his own dark times to enable him to get there...

Yes-these diseases are limiting--but in terms of culture--they do not prevent the additon of new ideas, new configurations of ideas and support for those who produce to have an impact.

It's a race really--see if we can solve the problem before we evolve to a state of total incusion-survivability of what once killed us, without utterly destroying the capacity of our environment to sustain us.

I think it's exciting and a worthy goal.

what he said. . .
he just made every point I could think of, but better!