3
votes
2answers
220 views

The number of nipples (breasts) a species has?

Only mammals have mammaries and mammary glands. What evolutionary factors determines the number of mammaries (nipples/teats/breasts) a species has? Is it always an even number?
7
votes
3answers
207 views

Is the appendix a vestigial structure in all vertebrates?

In humans the Appendix is a vestigial organ. Does it serve no apparent purpose in all the vertebrates that have one?