Saturday, January 12, 2019

Aging: "Yes, Life in the Fast Lane Kills You"


New insights into mitochondria reveal how life expends energy.
Nick Lane is an evolutionary biochemist at University College London who thinks about the big questions of life: how it began, how it is maintained, why we age and die, and why we have sex. Shunning the habit of our times to regard these as questions for evolutionary genetics, Lane insists that our fundamental biochemical mechanisms—particularly those through which living cells generate energy—may determine or limit these facts of life.

Lane has been steadily constructing an alternative, complementary view of evolution to the one in which genes compete for reproductive success and survival. He has argued that some of the big shifts during evolutionary history, such as the appearance of complex cells called eukaryotes (like our own) and the emergence of multicellular life forms, are best understood by considering the energetic constraints.

Lane’s book Life Ascending: The Ten Great Inventions of Evolution was awarded the 2010 Royal Society Science Books Prize, the top prize in the United Kingdom for books on science. His 2015 book The Vital Question: Why Is Life the Way It Is? has been described as “game-changing” and “brimming with bold and important ideas.” It offers a new, detailed model for how life might have begun by harnessing the incipient chemical energy at deep-sea vents. Bill Gates called The Vital Question “an amazing inquiry into the origins of life.”

Nautilus caught up with Lane in his laboratory in London and asked him about his ideas on aging, sex, and death.

In your book Power, Sex, Suicide you ask, “When did the drive for sex become punishable by death, and why?” What do you mean?
Sex evolved with complex cells. If we go back to bacteria, they don’t do sex as we know it. They do something similar—they swap genes, which is essentially what sex is doing: It’s moving genes around. But we’re combining them in different ways. The complex, eukaryotic cells, which include us, plants, fungi, and so on—all have sex. And that in itself is quite remarkable. But we don’t really know what the advantage of sex is. This is something that arose in evolution in this large group of complex cells. It seems to be necessary, and it’s linked tightly to death. The more we focus our resources on producing offspring, the better we will do in evolutionary terms. So if I focus all my resources on having sex, then effectively I take resources away from longevity. I take them away from surviving for longer, and so I shorten my lifespan almost deliberately in evolutionary terms.
There’s a cost to living; there’s a cost to doing everything.
What do you mean that sex is linked tightly to death?
Death in that sense is a specific process called programmed cell death. It’s controlled by the genes, it costs energy, and it’s very deliberate. Cells that have become damaged kill themselves and remove themselves and are often replaced with pristine new cells from the stem-cell population. Sex is doing that at the level of individuals by recombining genes. What that’s doing, in terms of natural selection, is increasing the differences between individuals. It’s increasing the variability in the population, and that aids natural selection. And what natural selection is seeing as the differences between people is back to sex again. How many offspring are you leaving? For us, that particularly means men. Selection is very biased toward a relatively small proportion of men leaving far more children.

You mean that some males do well and some do poorly?
Yes. What sex is doing at the level of selection is enabling the best genes to leave more copies of themselves. It’s increasing the variance in the population. So you have some very effective males and some fairly ineffective males, and it’s giving the opportunity to the more effective males. It’s not a very pleasant way of seeing the world from a human point of view. But that’s basically what evolution is doing.

You trace energetic processes down to a part of the cell called the mitochondrion. Where did mitochondria come from?
They were bacterium that got into another cell. There’s still argument about what that other cell looked like or was, but almost certainly it was quite a simple cell. And in the end the mitochondria became the power packs of our cells. So all the energy that we need to live is coming from the mitochondria.

How does this relate to aging?
There’s a cost to living; there’s a cost to doing everything. That cost depends on the speed at which we’re living, to some degree. If we are living our lives at a very fast rate, we tend to wear out sooner. There is a strong relationship between metabolic rate—the rate at which we’re taking in oxygen and burning up food—and lifespan. Under good conditions, we focus most of our resources on sexual maturation. I’m speaking not so much about humans as animals in general. But this goes beyond the animal kingdom....

This interview is the latest part of the series on aging.