quote:
If you do believe that all mammals share a common ancestor--would this have laid eggs--if so, wouldn't it continue to produce eggs (natural selection: if a mother is able to produce multiple young at once, the population grows much faster. Also, the young of egg-laying creatures don't depend on their mother's existence, whereas the young of creatures that develop in the womb--if the mother dies, so does the child!)
i know this post is a bit late in the discussion but whatever.
actually you have that a bit backwards. egg-laying animals don't lay lots of eggs so that they can reproduce faster and it's all happy and good that they don't have to care for the young.
rather. egg laying animals don't care for their young, so they have to lay lots of eggs in order to guarantee that some reach adulthood. animals that bear live young have a better chance of surviving to adulthood and those that bear live young AND care for their young to a well developed age have an even better chance at surviving. plus. animals that raise their young can pass on learned knowledge... eg they can learn to use tools and pass this on to the next generation.
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