Natural selection means Arabs should have a lower genetic risk of developing cataracts.
Arab culture shows why the opposite unexpectedly holds true.
Then we'll see this doesn't provide a contradiction at all.
Arab culture shows why the opposite unexpectedly holds true.
Then we'll see this doesn't provide a contradiction at all.
Natural Selection
Natural selection is when life evolves to cope with the negative features of their environment. Its Darwinian principles can be seen in all long-standing populations of all life forms, including humanity.
Polar bears are a good demonstration of this. They have fur and blubber to conserve heat. Also, polar bears are white for snow/ice camouflage, allowing them to better hunt their prey.
This principle also applies to humans. Tibetan blood carries oxygen more efficiently in order to cope with the lower oxygen levels at higher elevations. Adulthood lactose tolerance is prevalent in cultures that raise many dairy cattle.
Polar bears are a good demonstration of this. They have fur and blubber to conserve heat. Also, polar bears are white for snow/ice camouflage, allowing them to better hunt their prey.
This principle also applies to humans. Tibetan blood carries oxygen more efficiently in order to cope with the lower oxygen levels at higher elevations. Adulthood lactose tolerance is prevalent in cultures that raise many dairy cattle.
Let's look at Arabs: their biggest evolutionary pressure would be the dangers of the desert.
Various desert conditions (sunlight, heat, dehydration) can lead to cataract development. Cataracts make existence difficult at best and deadly at worst, especially for sight-dependent animals. So evolving to deal with the desert includes evolving to deal with cataracts.
Hence you'd expect desert dwellers, like Arabs, to have evolved to limit cataract development. Yet Arabs have a higher genetic risk for developing cataracts than many other ethnic groups.
The more related two people are, the more likely they are to share the same alleles (gene variants). Even bad alleles. So marrying relatives increases the chance of their offspring having two copies of the same bad allele and thus being negatively affected.
Perhaps Arabs, due to the prevalence of cousin marriages, have a higher rate of alleles that either encourage or can't prevent cataracts.
Various desert conditions (sunlight, heat, dehydration) can lead to cataract development. Cataracts make existence difficult at best and deadly at worst, especially for sight-dependent animals. So evolving to deal with the desert includes evolving to deal with cataracts.
Hence you'd expect desert dwellers, like Arabs, to have evolved to limit cataract development. Yet Arabs have a higher genetic risk for developing cataracts than many other ethnic groups.
Arab Culture
Arabs genes promote cataracts. Whilst initially at odds with natural selection, cultural practices do provide an explanation: cousin marriage.The more related two people are, the more likely they are to share the same alleles (gene variants). Even bad alleles. So marrying relatives increases the chance of their offspring having two copies of the same bad allele and thus being negatively affected.
Perhaps Arabs, due to the prevalence of cousin marriages, have a higher rate of alleles that either encourage or can't prevent cataracts.
Does this go against the idea of natural selection? Well, no.
Human intelligence leads to adaptive behaviours and items, reducing the negative consequences of our environment. Our intelligence is a product of our DNA, meaning that intelligence is the product of natural selection.
For example, Arab ingenuity adapts them for desert life. All the dangers of deserts lead to cataracts, so by dealing with desert risks, cataracts are less of a risk. So, whilst Arab DNA makes them more susceptible to cataracts, their DNA also allows them the intelligence to develop behaviours and tools to mitigate this risk.
Arab desert survival is impressive (as all clever things are). Loose garmets create shade and air circulation. Architecture creates shadows, promotes breezes and allows cooling via evaporation. Oral histories have allowed for the transmission of food and water sources. Activity is limited to the cooler parts of the day to avoid dangerous heat.
As such, behaviours to cope with cataracts and biology to prevent cataracts are equally good examples of natural selection. Just because Arabs rely on the former doesn't make their cataract-susceptibility a negation of Darwinian evolution.
Human intelligence leads to adaptive behaviours and items, reducing the negative consequences of our environment. Our intelligence is a product of our DNA, meaning that intelligence is the product of natural selection.
For example, Arab ingenuity adapts them for desert life. All the dangers of deserts lead to cataracts, so by dealing with desert risks, cataracts are less of a risk. So, whilst Arab DNA makes them more susceptible to cataracts, their DNA also allows them the intelligence to develop behaviours and tools to mitigate this risk.
Arab desert survival is impressive (as all clever things are). Loose garmets create shade and air circulation. Architecture creates shadows, promotes breezes and allows cooling via evaporation. Oral histories have allowed for the transmission of food and water sources. Activity is limited to the cooler parts of the day to avoid dangerous heat.
As such, behaviours to cope with cataracts and biology to prevent cataracts are equally good examples of natural selection. Just because Arabs rely on the former doesn't make their cataract-susceptibility a negation of Darwinian evolution.
No comments:
Post a Comment