Yep, with the notable exceptions of dogs and cats...
things are getting much clearer for me now. tnx again for your time.
No problem. If you have any other questions feel free to ask
Which form interesting exceptions, since they're not domesticated in quite the same way as the others - although, if one thinks about it, the dog, like the pig, is actually omnivorous, but otherwise fits the bill (as does the pig). Cats, of course, don't, but I suspect not everyone would agree that cats are domesticated, as opposed to merely being domestic.
Apparently the dog (or perhaps wolf) was the first animal to be domesticated. The idea goes that initially early humans would follow wolves which would lead them (inadvertently) to prey. The humans with their weapons were capable of taking much larger prey than the wolves could. Once the humans took their fill the wolves could scavenge what remained. Apparently then over time the symbiosis grew, becoming more organized.
Not so sure about cats. Perhaps we noticed having them around kept away rats etc.
Could this be an example of evolution in action?
Natural selection favoring the small it would seem.
Various shark species have been shrinking over the 400-million odd years that they've been around. Perhaps the more recent selective pressure is something to do with a shortage of food... The article cites human targeting of the larger individuals though.
Right, try this:
It's a couple of pages but it's a nice no-jargon kinda storybook version of speciation. It brings in the effects of mutation, habitat fragmentation and the main mechanisms of evolution itself and it shows how they combine to end up generating two species from one. It's done in a very basic, almost piss-take style but as a jumping-off point for discussion of speciation it's pretty good.
Hope that's a help.
It's interesting to consider that, over time, anthropogenic habitat fragmentation might well lead to a form of 'virtual' island dwarfism. I'm not sure if that has had time to develop anywhere as yet, though - possibly somewhere like England or other long-established anthropogenic environments.
bloody great idea for a thread. surprised it was never here before.
interesting thing in the bees article about how competing for social rank causes the brain to develop.
Would that mean that stratified society is actually making us more intelligent as we are forced to compete?
See the lost tribe of Pilau (National Geographic)
[Edit] Oops, my bad, was not anthropogenic, but it is interesting
That would depend on the nature of the competition. In modern human society, competition is almost entirely based on intelligence, but it's hard to say if we can yet observe evolutionary changes based on this due to the relatively short time scale.
But would it not be unreasonable to speculate that the hunting of larger specimens (to get the bigger fins), in a sense favouring them over the smaller ones, could be taking them out of the gene pool leaving the smaller ones to populate the species?
Of course this is all a bit hypothetical since whale shark breeding patterns are poorly understood at best. Their young and mating habits are virtually unknown. We don't yet know what age/size they reach sexual maturity at.
It's rather hard to say whether the reduction in the average size is actually representative of a change in the frequency of any specific genes without more extensive work. If larger sharks are being targeted and killed then we would fully expect the average shark size to reduce for that reason alone.