Even killer whales have their cute moments, as this photo of a mother and son together proves. This year, we learned that the prolonged life spans of killer whale moms and human mothers is due, in part, to caring for offspring -- especially sons.
"For most animal species, the potential for an individual to increase the propagation of its genes stops when they stop reproducing," Darren Croft, a senior lecturer in animal behavior at the University of Exeter, told Discovery News.
"Our results show that, as with humans, female killer whales can continue to increase the propagation of their genes long after menopause."
He added, "They do this by helping to increase the survival of their older sons, which in turn increases the number of grandchildren fathered by their sons. Through this process, evolution favors females that live longer after their menopause."