Kubrick & Hitchcock's Mom
Join Date: Apr 2007
Location: New York, NY
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Photo Submissions 33 Times in 24 Posts
Kara, yes you are right... small mutations can occur over time but your assumption that we are taller due to a genetic difference is not right. Think about it for a sec... a random mutation only occurs approximately every 1,000 bases. Now think of all the people who live in the US (for sake of argument), what would be the likelihood that they would all have the exact same random mutation to affect their size (height or whatever) at the same time? Really really really small.
The reason that is believed that people are taller/bigger nowadays is due to a MUCH better diet (especially during pregnancy - prenatal vitamins, no smoking or drinking, less caffeine and the such - basically everything your doctor told you not to eat/drink while you were pregnant that have been shown to affect the size of your baby) and better food. To a smaller extent, there are people who believe that all of the hormones that are placed into food to make them bigger can and do affects you and your body. I am not advocating organic food, or anything like that as I eat non-organic food myself, but that has been shown to be a more likely reason for people being taller now than a mutation in the entire population (as I said, very unlikely).
And yes, it's true... small genetic mutations COULD change color, size and differences to make the animal adapt but over 40 years?! The differences would be very small. I stress that I am talking about EVOLUTION, as you asked about... breeding (by humans) for a specific quality CAN produce the physical changes that you want over a much shorter time period.
In terms of evolution alone, except for the one or two odd dogs out (who got the correct mutation to affect their size, color, etc.) the large majority of the dogs will only have recessive mutations that will not change any aspect of their physical appearance. In order to do that, many many many generations have to pass with a heck of a lot of random mutations hitting the right gene. Animals adapt to conditions over HUNDREDS of years, not in decades.
Humans use the one or two mutations that pop up over generations, through inbreeding, to produce a dog that looks a certain way or has an interesting characteristic, or whatever. Breeding of dogs towards a specific characteristic is in short a way to cheat the many years of evolution and even to cheat it all together (producing a dog that is not necessarily healthy or viable for their environment and in the wild would die out - basic natural selection).
Last edited by Lina; 06-15-2007 at 10:31 AM.