An elephant never forgets

Animals almost always continue to reproduce until the day they pass away. However, there are three exceptions that have been discovered so far: humans, killer whales and short-finned pilot whales (Johnstone et al. 2010; Peccei, 2001; Flinn, 2013). The females of all three species live in large family groups, have matriarchs that transmit information about resources and demonstrate prolonged offspring care, however they lose the ability to have children, but continue to live for decades afterwards, thus signifying menopause.

Elephants provide their herd with the same benefits as humans, killer whales and short-finned pilot whales, so why has menopause not evolved within this species? “They are better at recognising welcoming faces and know the best anti-lion moves” (Yong 2015). Elephants differ from the other species such as the killer whales in one critical respect; in killer whales their daughters and sons remain within the same groups in which they were born. This means that’s when a female grows older, her pod becomes full of her own children and grandchildren. Over time, the female becomes increasingly related to her neighbours, and more genes are shared with her neighbours. This then creates a powerful impetus to shift her efforts away from having more offspring and towards helping existing descendants. 

Figure 1. Nowadays, only two original regions of elephants.Cr. Pinterest (2015)

This impetus does not exist in elephants as the sons eventually leave the birth group to discover new ones. Therefore, females become less related to their group-mates over time which leaves a matriarch’s to carry on reproducing until she passes away (Brent et al. 2015). “So, it’s not just about the dispersal patterns, but also the role that old females can play in the group,” says Croft.

https://www.youtube.com/watch?v=OrHiEYGqnEk

                          

References:

Brent, L.J.N., Franks, D.W., Cant, M.A. & Croft, D.P. (2015). Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales. Current Biology 25, 746-750. http://dx.doi.org/10.1016/j.cub.2015.01.037; Retrieved 12/04/2015.

Flinn, M.V. (2013). Are humans the only species that go through menopause? http://www.researchgate.net/post/Are_humans_the_only_species_that_go_through_menopause; Retrieved 27/03/2015.

Johnstone, R.A., & Cant, M.A. (2010). The evolution of menopause in cetaceans and humans: the role of demography, 277(1701):3765-3771. Doi: 10.1098/rspb.2010.0988.

Peccei, J.S. (2001). Menopause: Adaptation or Epiphenomenon. Evolutionary Anthropology, 10:43-57.

Pinterest, C. (2015). Howadays, only two original regions of elephants. http://www.mthai.com/en/lifestyle/10426.html; Retrieved 12/04/2015.

Powledge, T.M. (2008). The Origin of Menopause: Why Do Women Outlive Fertility? Scientific American, a division of Nature America, Inc.http://www.scientificamerican.com/article/the-origin-of-menopause/; Retrieved 04/04/2015.

Yong. E. (2015). Why Killer Whales Go Through Menopause But Elephants Don’t. http://phenomena.nationalgeographic.com/2015/03/05/why-killer-whales-go-through-menopause-but-elephants-dont/; Retrieve3d 12/04/2015.