Dysgenic Fertility - What does the evidence say?

[rousseau]

I was thinking about dysgenic fertility in the past few weeks, and was wondering what some of our members think of the evidence surrounding it. Basically it's the idea that some reproduction schemes can actually do stuff like reduce the intelligence of a population. I'm curious if this is happening, and what evidence on it exists.

One study:

Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time

People Getting Dumber? Human Intelligence Has Declined Since Victorian Era, Research Suggests

"The reduction in human intelligence (if there is any reduction) would have begun at the time that genetic selection became more relaxed," Dr. Gerald Crabtree, professor of pathology and developmental biology at Stanford University, told The Huffington Post in an email. "I projected this occurred as our ancestors began to live in more supportive high density societies (cities) and had access to a steady supply of food. Both of these might have resulted from the invention of agriculture, which occurred about 5,000 to 12,000 years ago."

 

[Treedbear]

I saw a tv show about the brain recently on PBS in which scientists claimed human brains were bigger when we were hunter gatherers because life presented many more problem solving demands than we face now in society. But then size isn't everything. They found a women in China who's cerebellum (which contains 80% of the brain's neurons) was completely missing, but since it was a congenital defect the rest of her brain compensated.

 

[Peez]

A working definition of "intelligence" is problematic, but leaving that aside...

An aspect of selection that people almost always ignore is that there are virtually always trade-offs. To put it simplistically, higher "intelligence" is not necessarily a "good" thing, because there is a cost to higher "intelligence" (e.g., more nerve tissue, more complex development that risks failure, longer development, etc.). If, given the current set of genes and the current environment, the benefits of greater "intelligence" outweigh the costs, then selection would favour greater "intelligence". On the other hand, if the costs outweigh the benefits, then lower "intelligence" could be favoured.

If a population finds itself in an environment different from the one it evolved in, then it is possible that the adaptive value of "intelligence" will be different, but it is also possible that the costs will be different. Certainly the balance between benefits and costs could change, but it is far from obvious which direction this change might take in the case of humans becoming more "civilized". One could argue that there is a stronger correlation between "intelligence" and reproduction in a hunter-gatherer culture, but one could also argue that the costs associated with "intelligence" are lower in a "civilized" culture.

Peez

 

[rousseau]

A working definition of "intelligence" is problematic, but leaving that aside...

An aspect of selection that people almost always ignore is that there are virtually always trade-offs. To put it simplistically, higher "intelligence" is not necessarily a "good" thing, because there is a cost to higher "intelligence" (e.g., more nerve tissue, more complex development that risks failure, longer development, etc.). If, given the current set of genes and the current environment, the benefits of greater "intelligence" outweigh the costs, then selection would favour greater "intelligence". On the other hand, if the costs outweigh the benefits, then lower "intelligence" could be favoured.

If a population finds itself in an environment different from the one it evolved in, then it is possible that the adaptive value of "intelligence" will be different, but it is also possible that the costs will be different. Certainly the balance between benefits and costs could change, but it is far from obvious which direction this change might take in the case of humans becoming more "civilized". One could argue that there is a stronger correlation between "intelligence" and reproduction in a hunter-gatherer culture, but one could also argue that the costs associated with "intelligence" are lower in a "civilized" culture.

Peez

In this case it seems to be less about the costs of intelligence, rather than the costs of being less intelligent. These days, because it's incredibly easy to produce offspring even with little material ability, those who wouldn't have otherwise reproduced stay in the gene pool, and they may even have more kids than they would have otherwise.

Living in poverty and still producing a line of descendants is very much a possibility. So the cost/benefit of intelligence aside, to me the pertinent thing is that a society which is good at protecting it's weakest members, paradoxically might also lower the average efficacy of it's population.

 

[Peez]

A working definition of "intelligence" is problematic, but leaving that aside...

An aspect of selection that people almost always ignore is that there are virtually always trade-offs. To put it simplistically, higher "intelligence" is not necessarily a "good" thing, because there is a cost to higher "intelligence" (e.g., more nerve tissue, more complex development that risks failure, longer development, etc.). If, given the current set of genes and the current environment, the benefits of greater "intelligence" outweigh the costs, then selection would favour greater "intelligence". On the other hand, if the costs outweigh the benefits, then lower "intelligence" could be favoured.

If a population finds itself in an environment different from the one it evolved in, then it is possible that the adaptive value of "intelligence" will be different, but it is also possible that the costs will be different. Certainly the balance between benefits and costs could change, but it is far from obvious which direction this change might take in the case of humans becoming more "civilized". One could argue that there is a stronger correlation between "intelligence" and reproduction in a hunter-gatherer culture, but one could also argue that the costs associated with "intelligence" are lower in a "civilized" culture.

Peez

In this case it seems to be less about the costs of intelligence, rather than the costs of being less intelligent. These days, because it's incredibly easy to produce offspring even with little material ability, those who wouldn't have otherwise reproduced stay in the gene pool, and they may even have more kids than they would have otherwise.

Living in poverty and still producing a line of descendants is very much a possibility. So the cost/benefit of intelligence aside, to me the pertinent thing is that a society which is good at protecting it's weakest members, paradoxically might also lower the average efficacy of it's population.

You seem to be assuming that “intelligence” is correlated with wealth, but this is not evident. To address this issue, a precise definition of “intelligence” would have to be agreed upon. I suspect that there are several different traits that we tend to lump together in “intelligence”, and some of these traits may even be negatively correlated with each other. It is certainly conceivable that selection may now be favouring certain traits associated with “intelligence”, but it is probably easier to argue simply that selection on “intelligence” is relaxed: there is little or no correlation between “intelligence” and reproductive rate. This would leave “intelligence” in the grip of genetic drift.

I am not sure if I see a paradox here. Protecting the “weakest members” is not meant to increase the “efficiency” of the population. This is where the shadow of eugenics starts to creep in, but genetic engineering may allow us to avoid that (of course genetic engineering comes with its own ethical issues).

Peez

 

[rousseau]

A working definition of "intelligence" is problematic, but leaving that aside...

An aspect of selection that people almost always ignore is that there are virtually always trade-offs. To put it simplistically, higher "intelligence" is not necessarily a "good" thing, because there is a cost to higher "intelligence" (e.g., more nerve tissue, more complex development that risks failure, longer development, etc.). If, given the current set of genes and the current environment, the benefits of greater "intelligence" outweigh the costs, then selection would favour greater "intelligence". On the other hand, if the costs outweigh the benefits, then lower "intelligence" could be favoured.

If a population finds itself in an environment different from the one it evolved in, then it is possible that the adaptive value of "intelligence" will be different, but it is also possible that the costs will be different. Certainly the balance between benefits and costs could change, but it is far from obvious which direction this change might take in the case of humans becoming more "civilized". One could argue that there is a stronger correlation between "intelligence" and reproduction in a hunter-gatherer culture, but one could also argue that the costs associated with "intelligence" are lower in a "civilized" culture.

Peez

In this case it seems to be less about the costs of intelligence, rather than the costs of being less intelligent. These days, because it's incredibly easy to produce offspring even with little material ability, those who wouldn't have otherwise reproduced stay in the gene pool, and they may even have more kids than they would have otherwise.

Living in poverty and still producing a line of descendants is very much a possibility. So the cost/benefit of intelligence aside, to me the pertinent thing is that a society which is good at protecting it's weakest members, paradoxically might also lower the average efficacy of it's population.

You seem to be assuming that “intelligence” is correlated with wealth, but this is not evident. To address this issue, a precise definition of “intelligence” would have to be agreed upon. I suspect that there are several different traits that we tend to lump together in “intelligence”, and some of these traits may even be negatively correlated with each other. It is certainly conceivable that selection may now be favouring certain traits associated with “intelligence”, but it is probably easier to argue simply that selection on “intelligence” is relaxed: there is little or no correlation between “intelligence” and reproductive rate. This would leave “intelligence” in the grip of genetic drift.

I am not sure if I see a paradox here. Protecting the “weakest members” is not meant to increase the “efficiency” of the population. This is where the shadow of eugenics starts to creep in, but genetic engineering may allow us to avoid that (of course genetic engineering comes with its own ethical issues).

Peez

I don't mean to suggest that this is a moral problem that needs to be fixed. I'm just curious if it's actually happening.

I don't know that I share your view that we don't have a working definition of intelligence. At its core intelligence is the ability to use known information to solve novel problems. It's just also true that this variable in itself isn't predictive of behavior without accounting for a host of other mental traits.

People with greater general intelligence *are* wealthier and more successful averaged out, it's just not a guarantee of success by itself.