December 16, 2013
Forever Young: Several Species Resist Senescence
Have you ever looked in the mirror and wished you could turn back the tides of time? My sister is about ready to graduate college, and in a futile attempt to remain in glorious denial, I’ve taken to calling her “kiddo.” She’s a good sport about it (when she’s not reminding me that I’m past halfway to fifty), but the jest serves as a somber reminder of the one thing none of us can escape: time. While I’m certainly not to the point of sitting out on a porch with a shotgun, shooing away “durned whippersnappers,” I’ve certainly felt the passage of time in my own way. At risk of sounding morbid, eventually it will catch up to me. As humans age, we degrade. Eventually, we simply stop working. It’s just a fact of life. But not all life.
The fancy scientific word for that phenomena is “senescence,” which refers to the cumulative changes to our molecules and cells, specifically those that disrupt metabolism, as time goes on. A recent study, however, suggests that not all creatures in the animal kingdom are shackled to the sands of time as we humans. Biologist Owen Jones of the University of Southern Denmark led the study, kicking it all off with a compilation of data sets recording fertility, mortality, and age amongst dozens of different species. In order to account for species with naturally short lifespans such as certain insects and plant life, the mortality rate of each individual organism was divided by the average mortality rate of the species, creating a singular unit through which all the lifespans could be compared. According to Jones, this cross-species examination revealed several species that contradicted the traditional notion that evolution always leads to senescence.
The findings are especially intriguing considering the link between age and weakness was previously assumed to be hardwired within the cycle of nature itself: things are born, grow old, wither, and die. While everything does eventually die (no one’s arguing that point), the intriguing factor was the consistent level of fertility and sporadic nature of mortality amidst some of the studied species. Take, for example, the freshwater medusa (the fancy name for which is Hydra magnipapillata). This underwater invertebrate was found to live for hundreds of years with no notable decrease in fertility, activity, or cellular efficiency. Even stranger is the desert tortoise (Gopherus agassizii), a creature that gets stronger as it ages. The mortality rates of these tortoises actually decrease the longer it is alive, completely contrary to what we assume about old age. Consider me officially jealous.
Unfortunately for those longing to escape time’s inevitable grip, this discovery is more an intriguing look at what already happens than a step towards eternal youth or immortality. In the end, that’s probably a good thing. I imagine being immortal would be incredibly boring … at least after the first century or two.
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