e generational length. Petty’s primogeniture model may have been true to law and custom for land inheritance, but it is not true to biology. I prefer R. A. Fisher’s? method equal-weighting all births from first to last, and equal-weighing ages of both parents at each birth. We have some evidence that the maternal

c respectively meant fitness given up by the investor and fitness grained by the investee. He further made it clear that fitness could be measured as R. A. Fisher’s “reproductive value” V(x) published in 1930 and 1957. V(x) meant likelihood at age x of reaching each successive age times expected offspring at tha