Trade-offs between studliness and survival keep less endowed sheep in the mix
Sometimes it pays to be mediocre. A new study shows that sheep with a 50/50 blend of genes for small and big horns pass along more of their genes over a lifetime than their purely big-horned brethren, who mate more often.
The finding offers rare insight into an enduring evolutionary paradox—why some traits persist despite creating a reproductive disadvantage.
The results, published online August 21 in Nature, reveal that while big-horned sheep mated most successfully each season, small-horned sheep survived longer. Rams who inherited one of each type of gene from their parents got the best of both worlds: they lived longer than bigger-horned sheep and mated more successfully than those with the smallest horns.
As a result, middle-of-the-road sheep passed on more of their genes over time. “They’re the fittest of them all,” says Jon Slate of the University of Sheffield in England, who led the study.