fossil y exsited during the same period a ammonite
I believe all of the above!
Half, because the ovum from the mother and the sperm from the father fuse together to form the zygote which will develop into the new human being, and the ovum and sperm, being gametes, each have half the number of chromosomes that you usually find in somatic cells (any other cell in the body that is not a gamete).
