Penis
Domestic cats have barbed penises, with about 120–150 one millimeter long backwards-pointing spines. Upon withdrawal of the penis, the spines rake the walls of the female's vagina, which is a trigger for ovulation. Lions also have barbed penises. Male felids urinate backwards by curving the tip of the glans penis backward. When male cheetahs urine-mark their territories, they stand one meter away from a tree or rock surface with the tail raised, pointing the penis either horizontally backward or 60° upward.
Brain size
Studies on human brain size, largely based on participants of European ancestry, tend to find an average adult brain volume of 1260 cubic centimeters (cm) for men and 1130 cm for women. There is, however, substantial variation between individuals; one study of 46 adults, aged 22–49 years and of mainly European descent, found an average brain volume of 1273.6 cm for men, with a range of 1052.9 to 1498.5 cm, and 1131.1 cm for women, with a range of 974.9 to 1398.1 cm.