Hello Jeanie,

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... but isn't this issue rather rediculous? Olive skin or a propensity to tan well is inherited, but babies can't be born with TANS. They may have dark skins.... ????????????
Of course, it was ridiculous on the first post by Russ, with comic episodes from CTD added to the mix.

People will have normal genetic variations in the darkness of their skin, and they will have normal genetic variations in their ability to tan, however these are determined by your genes and not your behavior.

Natural selection can make darker skins and ability to tan advantageous, and lead to greater ability to survive and reproduce (ever tried to enjoy sex while badly sunburned? Ever had a sunburn so bad it made you sick?) and sexual selection can cause some people to be selected for mating over others that are not as tanned (or those without naturally darker skins).

This will not pass on their tans to offspring, but their skin color and ability to tan that is in their genes will be passed on. As selection proceeds, everything else being equal (it rarely is), it will shift the frequency of the hereditary traits from those that are light skinned or tan poorly to those that are darker skinned or tan easily so that the population as a whole will appear darker/tanned.

The problem that Lamarkism faces (and Neo-Lamarkism with it) is that you need to have a mechanism to transmit change to following generations. So far the only mechanism known is through the DNA offspring inherit from their parent/s.

Acquired traits like tanned skin can be passed on by behavior (time spent tanning, makeup), but not by genes, and they do not survive the removal of the behavioral trait.

Selection for survival and reproduction based on acquired traits will select for continued behavior (time spent tanning, applying makeup), AND it will also select for those in the population that have natural variations that enable them to tan - the genetic variations within the population that are also part of the phenotypes that are selected. As selection proceeds, everything else being equal (it rarely is), it will shift the frequency of the hereditary traits from those that are light skinned or tan poorly to those that are darker skinned or tan easily so that the population as a whole will appear darker/tanned.

Enjoy.

Last edited by RAZD; 09/14/08 07:07 PM. Reason: clarified