565 Million Age, in years, of the fossils of soft-bodied tubular organisms in South Australia that provide the earliest evidence of sexual reproduction. The fossils, described in 2008, are attached to the seafloor in groupings that resemble the clustered pattern of today’s sexually reproducing corals and sponges.
7 Number of different sexes of Tetrahymena thermophila, a single-celled organism found in pond water. The diversity may help maximize the chances of finding a mate: An individual can reproduce with members of any sex except its own, leading to 21 possible couplings. Other organisms achieve even headier numbers. The slime mold Physarum polycephalum exists in more than 700 mating types, though not all of them are sexually compatible.
8:1 Ratio of the length of a barnacle’s penis to the rest of its body, making it proportionally the largest phallus in the animal kingdom. Barnacles need an unusually long appendage in order to ...
