spotfin;3496385; said:
In a captive environment though, all pups in a litter have a better chance of survival because we are able to provide for them regardless of their fitness. Could this lead to future generations that have a lowered fitness level?
The simple answer: no.
The fine print: Yes, any present inheritable weaknesses in your breeding population are going to be passed down, and are more likely to evenly propogate in the gene pool than they otherwise would be. The easy solution to that would be to breed only healthy individuals. The fact is that to see meaningful genetic drift or new weaknesses emerge we would have to be doing captive breeding for time scales measured (conservitatively) in the thousands of years*. We’re talking about the fringes of geologic time. Think continental drift. (Also, a buffering factor in this would be that the healthy traits would presumably still provide some slim benefit, or at least would not hinder the individual’s chances at reproduction.)
While what you are talking about is technically possible, it isn’t something that we need to worry about on this scale. This fear is much akin to fearing that a sapling tree may impale you while it grows during your morning walk. Trees grow much too slowly to be dangerous, obviously, although they can appear quite violent in time-lapse growth (especially when they get into a ”shoving” match with another tree over access to sunlight.)
*This (more) natural selection should not be confused with outright deliberate fitness or trait-based artifical selection. Simply allowing individuals to breed, and not choosing individuals based on specific traits, would not change the gene pool in any measurable degree for quite some time. This cannot be said if deliberate traits are selected for in breeding, such as in the case of modern cattle, horses, bananas, or almost anything else that we eat, ride, milk, grow, or bet money on.
