1.   Even when animals look normal at birth, genetic glitches can show up later.

2.   The genetic glitch that causes sickle cell disease, for example, protects against malaria.

3.   Researchers believe those genetic glitches can be corrected if the gene pool expands.

4.   Sprouting two heads results from flawed embrionic development, probably because of a genetic glitch.

5.   The survivors later were traced to three mothers, which may have created genetic glitches in the current population, slowing their reproduction.