Talk:Natural selection/Archive 7

message: If we are serious about coming up with a good lead paragraph, I think that two things have to happen:
#We have to realize that we are not really arguing about the core principle of Natural Selection.  I believe we are in agreement, even if we may not want to admit it.  What we differ in is the approach.  Population geneticists tend to use a "bottom-up" approach, which involves working on the parameter space of the problems, and, in some ways, leaving the genotype->phenotype connection to the estimation of those parameters.  Ecological geneticists take a "top-down" approach, which involves working extensively in the phenotype space of the problems, with obvious concerns about understanding the phenotype->genotype connection.  For the most part, we can leave out Darwin altogether, other than for historical interest.  Darwin's ideas of Natural Selection were accomplished without a correct understanding of inheritance (pre-Mendelian).
#The condescending attitudes have to stop.  Both approaches are used today by modern, albeit by different, researchers.  They are both valid approaches, and they are both useful.  Because the core principle of Natural Selection is the same, we should be able to find that core principle, then talk about how the various approaches are different.
The alternative is continuing to argue continuously and pointlessly. TedTalk/Contributions 12:28, 6 July 2006 (UTC)
replies: text: This is very well possible, but also think about maternal effects, leaning, dominance, epistatsis, GxE, etc. -- Kim van der Linde at venus 15:43, 7 July 2006 (UTC)

text: You're quite right Axel, and I can see that there is a looseness here. A trait doesn't really mean anything useful unless you think of it strictly as a phenotypic feature that varies between individuals in a population. So the important question is not whether all traits are determined by genes, obviously they all are, but how much of the inter-individual variation in traits is genetic, and for some traits all the relevant variation may be non-genetic. Any suggestions?Gleng 15:49, 7 July 2006 (UTC)
replies: text: The first of Mendel's postulates is that traits are unitary.  One of the traits he studied was dwarfism.  The genius of his postulate is that there is quite a bit of variability of height in pea plants, both genetic and environmental, but it is obvious when the plant is dwarf or normal.  Albinism (tyrosinase-, if you want to limit it to specify a single gene) is a unitary trait. However, not all tyrosinase- albinos have exactly the same skin or hair color, but you can quickly identify the albinism genotype (even between tyrosinase+ and tyrosinase- if you are good at it).  Mendel was going beyond the phenotype to look at the genotypes.  In real and meaningful ways, every gene is affected by lots of other genes as well as the environment.  How you treat those differences is dependent on your approach to genetics. TedTalk/Contributions 16:59, 7 July 2006 (UTC)
thread_title:  If we are serious about this 

message: The sentence in the overview is 'some traits are determined by just a single gene, but most are affected by many different genes.' But is this correct? Marcosantezana once said in this talk 'the fitness-wise most important phenotypic variation is either genetic but not heritable in the narrow sense or is not genetic at all'. Kim has expressed similar views in separating selection from response. — Axel147 13:59, 6 July 2006 (UTC)
replies: text: This is very well possible, but also think about maternal effects, leaning, dominance, epistatsis, GxE, etc. -- Kim van der Linde at venus 15:43, 7 July 2006 (UTC)

text: You're quite right Axel, and I can see that there is a looseness here. A trait doesn't really mean anything useful unless you think of it strictly as a phenotypic feature that varies between individuals in a population. So the important question is not whether all traits are determined by genes, obviously they all are, but how much of the inter-individual variation in traits is genetic, and for some traits all the relevant variation may be non-genetic. Any suggestions?Gleng 15:49, 7 July 2006 (UTC)
replies: text: The first of Mendel's postulates is that traits are unitary.  One of the traits he studied was dwarfism.  The genius of his postulate is that there is quite a bit of variability of height in pea plants, both genetic and environmental, but it is obvious when the plant is dwarf or normal.  Albinism (tyrosinase-, if you want to limit it to specify a single gene) is a unitary trait. However, not all tyrosinase- albinos have exactly the same skin or hair color, but you can quickly identify the albinism genotype (even between tyrosinase+ and tyrosinase- if you are good at it).  Mendel was going beyond the phenotype to look at the genotypes.  In real and meaningful ways, every gene is affected by lots of other genes as well as the environment.  How you treat those differences is dependent on your approach to genetics. TedTalk/Contributions 16:59, 7 July 2006 (UTC)
thread_title: Small point overview paragraph