Dawkins: Not One of Our Ancestors Was a Failure

Richard Dawkins’s theme is upbeat:

All organisms that have ever lived—every animal and plant, all bacteria and all fungi, every creeping thing, and all readers of this book—can look back at their ancestors and make the following proud claim: Not a single one of our ancestors died in infancy. They all reached adulthood, and every single one [allowing for the inclusion of such outliers as in vitro fertilization] was capable of finding at least one heterosexual partner and of successful copulation. Not a single one of our ancestors was felled by an enemy, or by a virus, or by a misjudged footstep on a cliff edge, before bringing at least one child into the world. Thousands of our ancestors’ contemporaries fail in all these respects, but not a single solitary one of our ancestors failed in any of them.…Since all organisms inherit all their genes from their ancestors, rather than from their ancestors’ unsuccessful contemporaries, all organisms tend to possess successful genes. They have what it takes to become ancestors—and that means to survive and reproduce…That is why birds are so good at flying, fish so good at swimming, monkeys so good at climbing, viruses so good at spreading. That is why we love life and love sex and love children. It is because we all, without a single exception, inherit all our genes from an unbroken line of successful ancestors. (River Out of Eden)

Many readers love this passage. Its any-organism’s view backwards along the unbroken line of forebears celebrates the successes and joys of being alive. And it explains this success not as the result of human uniqueness or a generous deity but as nature’ own selection process. The same pride and pleasure we take in hearing about a great-grandmother who struggled, travelled, settled, and raised a family, Dawkins extends to all ancestors of all species, without exception. Any reader who may have earlier viewed evolution as alien and godless might feel a little less resistance now.

But other readers may take exception to the passage for other reasons. Some of that inheritance from our successful ancestors, we wish we would be spared. Down Syndrome, Cystic Fibrosis, some cancers, and other diseases are inherited to a degree. So are mental illness and violent tendencies. For those suffering from such inheritances today, the genetic filter has not been effective enough.

And then there’s bad luck. Many organisms that were as well-endowed genetically as “successful” ancestors might also have left offspring had it not been for factors beyond their control. The twin of that pioneer grandmother may have died in battle, gone down with the ship, succumbed to an earthquake, or starved in a drought—childless.

Last but not least, many people today are able to have children but choose not to. They may remain, though, no less “successful” in every other sense of the word.

In the end, I think these exceptions, instead of weakening Dawkins’ point, strengthen it—as if each living organism could say with conviction, see, so many different pieces, not only the genes but the circumstances too, had to fall into place for me to be here. And they did.

 

 

 

Survivors and the Terminator

The story of biological evolution recounts the ways that most plants and animals have changed over time as small bodily variations improved their odds of survival. But what about those species, fitted successfully to stable environments early on, that have changed very little? Are any such ancient species (besides the microbes) still around today?

Yes. In Survivors: The Animals and Plants that Time Has Left Behind, Richard Fortey tracks down some present-day creatures that look much like their fossilizeds ancestors from millions of years ago. Oddly, their stories of sameness impress me with as strong a sense of evolution’s power as the stories of other species, including ours., that have changed to adapt.

Horseshoe crabs, after half a billion years, still crowd the beach. (delaware-surf-fishing.com)

Horseshoe crabs, after half a billion years, still crowd the beach.
(delaware-surf-fishing.com)

In the opening chapter, Fortey is on a beach in Delaware on the night of the annual horseshoe crab orgy, when thousands of male horseshoe crabs come ashore to clamber on top of the females. Horseshoe crabs have  been scrambling up beaches for 500 million years.

In the darkness along Delaware Bay the scratching percussion of the crabs provides an unmusical accompaniment on an imaginary journey backwards in time: to an era well before mammals and flowering plants; a time before the acme of giant reptiles, long before Tyrannosaurus; backwards again through an extinction event 250,000,000 years ago that wiped nine-tenths of life from the earth; and then back still further, before a time of lush coal forests to a stage in the earth’s history when the land was stark and life was cradled in the sea.

firmoss (newfs.s3.amazonaws.com)

Four hundred mya, plants like this Norwegian Huperzia moved from the water to land and were among the first to acquire the crucial, stiffened water-conducting tubes that enabled them to stand upright and compete for light.
(newfs.s3.amazonaws.com)

In the other chapters, Fortey describes the velvet worm in New Zealand, the lovely Norwegian fir moss, the not-so-lovely lungfish. The photo captions here mention their particular keys to adaptive success.

It helps that their environments have changed very little. “Survival is about endurance of habitat.” One habitat that endures is the tidal flat, where the shallow sea meets the muddy shore. Organisms here can burrow, find oxygen in the water and air, find food through filtering or scavenging. Here are horseshoe crabs, snails, small fish, many plants. “This habitat does seem like a good place to be for an organism with conservative tendencies. If its own place survives, then so will the beast. It is the right place to weather mass extinctions that affect many other environments more severely.…Stick-in-the-muds last longest.”

As for the durable species themselves, a few characteristics recur. “Many…seem to have long life spans.” Horseshoe crabs take a decade to mature. And some enduring animals invest more resources in fewer progeny by producing “relatively large eggs or few offspring.” But there are no fool-proof formulae. “[T]he luck for old timers will eventually run out. It always does.”

lungfish (media-web.britannica.com)

In Australia, Fortey finds the lungfish that dates back 400 mya, “the great survivor among the vertebrates, the animals with backbones.” With lungs, these sea creatures, in the transition to the land, can gulp air when the river runs low on oxygen.
(media-web.britannica.com)

What about humans? When will our time run out? Fortey doesn’t make guesses, but he has a hard label for us.

[Early man] may have hunted edible mammals and birds to the point of obliteration even in his earliest days; he was the first species that deserves to be called the Terminator….The extinction event that is happening right now is the first one in history that is the responsibility of a single species. There’s no meteorite this time, no exceptional volcanic eruptions, no ‘snowball earth,’ just us, prospering at the expense of other species.

He is confident about the survival of only one type of organism. “I am not worried about the survival of bacteria. They will be there to rot down the last bodies of the last humans, and then the wheel of life will have turned full circle.” So ends the book.

 

Feeling Old? Envy the Lobster

The certainty of death is hard enough. But aging as a prelude—the wrinkling, weakening, deteriorating and the rest of the assault—can feel downright demeaning! Is there a benefit here for survival of the species, or for any species, that no one told me about before I reached 73?

lobster (anvilcloud.blogspot.com)

(anvilcloud.blogspot.com)

Not all species go through their version of this. The paths that organisms follow after maturity vary enormously. Some plants live for one year only, others come back every season. Bacteria clone themselves and don’t die from age at all but from hostile organisms and conditions in their environment. Seabirds age very slowly; as long as they can fly, they can stay ahead of most predators.  Lobsters don’t age; they can continue to grow and remain fertile for 45 years or more in the wild, dying only when they can no longer molt and grow a larger shell.

How and why the declines of aging are included in the final phases of some species’ lives is complex. Wikipedia’s “Senescence” introduces the range of theories and uncertainties. Here are three insights from the evolutionary perspective that make sense to me.

One is that certain harmful genetic mutations switch on later in life after an organism’s reproductive period has ended. Many cancers in humans do, for example. Because they don’t impact the number or health of the offspring, such genes do no harm to the persistence of the species and so they are unlikely to be lost over the generations. The diseases of the elderly get passed along by the young.

Even more unfortunately, some mechanisms in our bodies boost our health when we’re young and then come back to bite us when we get older. Digesting calcium, for instance, builds strong bones early on but helps clog and stiffen arteries decades later. As long as such a function improves our fitness to make and raise babies, whatever damage it does later on doesn’t matter much in the very long run.

A third way in which selection seems indifferent to the pains of aging is statistical: even if natural selection did reduce the ravages of aging and prolong the fertile period, the population of such organisms would still decline with age as accidents and predators took their inevitable toll. The body invests its resources where they are the most effective for the future, in youth and early reproduction, not in a comfortable old age.

In these ways and others, aging is linked to the importance of reproduction and the dangers of predators and other external forces. For primates, including me, we reproduce early because the big cats—leopards, jaguars, cougars, tigers—stalked us for millions of years in the forests and grass lands. And for most other species as well, the safest bet for species continuity is simple: reproduce early. Still, the exceptions are fascinating. Lobsters in their suit of armor run little risk from ancient predators, so they can reproduce throughout their lives without ever aging into genetic irrelevance.

So, armed with such insights, do I experience my weakening muscles, declining sexuality, distracted thinking,  and dulled senses with any less resentment? Yes, a little. Knowing that the decline has its place, even though it’s a melancholy one, in the evolution that brought me to being in the first place is some consolation.