RE: Hen gives birth to chick without egg!
April 20, 2012 at 4:18 pm
(This post was last modified: April 20, 2012 at 4:20 pm by Anomalocaris.)
(April 20, 2012 at 2:58 pm)Phil Wrote:(April 20, 2012 at 11:30 am)downbeatplumb Wrote: http://www.bbc.co.uk/news/17769677
Quote:A Sri Lanka hen has given birth to a chick without an egg, in a new twist on the age-old question of whether the chicken or the egg came first.
Instead of passing out of the hen's body and being incubated outside, the egg was incubated in the hen for 21 days and then hatched inside the hen.
The chick is fully formed and healthy, although the mother has died.
Evolution in action ?
No evolution. The article says there was an egg inside the body. Evolution would be if there was no egg. What we have here is roughly a Chicken having a tubal pregnancy.
If tubal pregnancy has heritable genetic causes, it can certainly trigger evolution if there is selection pressure for it. I am hard pressed to come up with selecttion pressure favoring tubal pregnancy
But eggs hatching inside body (ovaviparity) is a distinctly different mode of reporduction for the purposes of survival fitness compare to eggs hatching after being laid outside the body, and paleotonolgy shows ovaviparity confer clear advantages to many branches of fishes and reptiles, and has evolved seperatelly over and over again in different branches.
Indeed some branches, like Ichtyosaurs, could never exist without the evolution of ovaviparity.
So it is less farfethed to say if ovaviparity appears in chickens, and it is heritable, then it could be an observed first part of a major evolutionary step in the chicken family.
