Why Do Elephants Seldom Get Cancer?

or it could be nonchalantly protecting you from cancer. There's no telling. Here's the thing, evolution doesn't have some great plan for you personally, whether or not you have genes that tell your palms to grow whiskers or your body to fight cancer. That's mostly just happenstance, mostly, but from time to time, DNA has been known to pull incredible hail Mary's Take elephants, for instance, they very rarely get cancer. An elephants cancer mortality rate is just under five percent.

For US humans it's between eleven and twenty five. Whales have very low rates of cancer too. In fact, large animals of all kinds seem to succumb to cancer way less than one might imagine. This puzzled cancer researchers in the nineteen fifties and sixties because the early understanding of why cancer happens has to do with how many cells an animal has, coupled with its longevity. Large and long lived animals, scientists theorized, have lots of cells and more

time in which cells could potentially start doing their jobs wrong. Conversely, small animals have fewer cells and generally don't live as long as larger animals. Thus there are fewer chances and less time for cells to mutate in the ways that

would result in cancer. This line of reasoning makes a good bit of sense, right Yet in the nine seven these, statistical epidemiologist Richard Peto observed that we don't see a higher instance of cancer in humans than we do in mice, even though human bodies contain a thousand times more cells and we live thirty times as long. And so science was introduced to Peto's paradox, the mystery that's bedeviled cancer

researchers for nearly half a century. Even though cancer reliably shows up in larger individuals within a species more often than in smaller ones. For instance, just a couple inches of height on a human can significantly raise her chances of getting some types of cancer. For whatever reason, huge and long lived animals have cancer rates comparable to or lower than our own. Because being humongous has evolved in various animals countless times over the eons, there are probably

as many solutions to Peto's paradox as there are gigantic animals. However, a study published in an August issue of Cell Reports found the reason for Peto's paradox and elephants is in reality completely bonkers genetically speaking. Previous research reported that African savannah elephants have a whole bunch of copies of a specific cancer fighting gene called t P fifty three. This gene produces a protein that comb cells looking for potential

DNA damage. Humans and most other animals have only one copy of this gene. Elephants, it happens, have twenty copies. So t P fifty three lends the elephant a lot of capacity to see that there is a problem, but not really the ability to do anything about it. So the University of Chicago research team rummaged around and the elephant genome to see if they could find any clue as to what would be carrying out the cell repairs or cell destruction that gives elephants their cancer fighting powers,

and they found something pretty obvious. Elephants have between seven and eleven copies of a type of gene known as leukemia inhibitory factor, or l i F. The problem was these copies were evolutionarily old, and many of them had probably been useful to the elephants distant ancestors, but they were so degraded that they were probably useless. But this is where things start getting weird. For the article this

episode is based on how Stuff Work. Spoke with the studies lead author one Manuel of as Quez, then a graduate student in the Department of Human Genetics at the University of Chicago. He said, well, what we actually found was a copy of l i F l i F six, which had integrated into the genome in the common ancestor of elephants and manatees. Manatees still have this piece of DNA, but it's what would traditionally consider junk. But elephants took this junk DNA and right before law lost any in

all coding potential for the correct protein. It evolved a new way of inducing its activation and expression into a functional protein. Again, it was pure luck. So as a last ditch attempt to cut down on the accumulation of bad cells, the elephant's body resurrected a piece of DNA that's capable of killing cells that have been flagged for execution by t P fifty three due to DNA damage

and put it to work culling those cells. L i F six kill cells by poking holes in the mitochondria, the power plant of the cell, and you know it could have gone wrong. What's amazing is that the elephant was able to both reactivate the gene and control it to tell l i F six to kill not every cell, but just the ones that seemed the most dangerous. You can't control your DNA, but sometimes it can come out with some pretty good tricks you'd never even think of.

Today's episode is based on the article Zombie Jeane protects Elephants from cancer on House Tofworks dot Com, written by Jesslyn Shield. Brain Stuff is production of I Heart Radio in partnership with housetuffworks dot Com, and it's produced by Tyler Clang. Four more podcasts on my heart Radio, visit the iHeart Radio app, Apple podcasts, or wherever you listen to your favorite shows.