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.

 

Hindus Seek Detachment. Have Plants and Animals Already Found It?

Here in suburbia, next to a glassy corporate office, sits a Hindu temple, its white, ornate façade surrounded by parking lots. Curious, I removed my shoes and walked into the large room. Instead of chairs or benches I found a marble, white and gold room with altars placed throughout. Worshippers strolled from one garlanded deity to the next, circling them several times or standing before them with hands together, eyes closed, heads lowered.

hindu temple inside (blogs.bootsnall.com

(blogs.bootnall.com)

Along the walls was a frieze of passages from the Bhagavad Gita, the dialogue between the god Krishna and a warrior about to enter battle, Arjuna. I walked beneath Krishna’s words about detachment:

He who hates no creature, who is friendly and compassionate to all, who is free from attachment, balanced in pleasure and pain, and forgiving…is dear to Me.

He by whom the world is not agitated and who cannot be agitated by the world, who is freed from joy, envy, fear, and anxiety—is dear to Me….

He who neither rejoices, nor hates, nor grieves, nor desires, renouncing good and evil, full of devotion, is dear to Me.

He who is the same to foe and friend, and also in honor and dishonor, who is the same in cold and heat and in pleasure and pain, who is free from attachment, to whom censure and praise are equal, who is silent, content with anything, homeless, steady-minded, full of devotion—that man is dear to Me.

I left the temple soothed by the place and by the words, by the invocation of a calm that does not take sides or react or pursue.

In my backyard later, I wondered whether nature sends us the same message of the value of steadfastness that Krishna proclaims. Can the non-theist find in other living things a model of that centeredness that rises above dualities?

(ivillage.com)

(ivillage.com)

I’m not sure. The backyard is a calm place, but even in winter the creatures there are hardly without their “attachments.” Birds search constantly for food and for each other. The trees and bushes and grass, though less agitated, are hardly “content with anything.” They wilt in a drought and burst with life when the environment is kind. They are different in good circumstances and bad, very different. What would Krishna say?

He might observe that plants and animals follow their in-born programs with no distracting superstructure of plans, preferences, or judgments. He would probably say that, except for humans and some animals, other living things may struggle and even kill but they don’t hate, they may shy from danger but they aren’t riven by anxiety, they may react differently to cold and heat but only at the basic physiological level.

So perhaps in the backyard I am looking at an imperfect but good lesson in how beings can do the work of staying alive and yet remain undistracted and unconfused. Can the human non-theist find a model of detachment in other living things? Partly, yes.

The Pioneers: Archaea and Bacteria

For many years I shared the common belief that living things fall into three or four basic categories. Besides plants and animals, one or two others groups with names that varied over the years—Bacteria, Protists, Prokaryotes— consisted of creatures too small to see.

phylogenetic tree wikipedia

In this evolutionary genetic tree, animals and plants, in the upper right corner, are not the main limbs.         (Wikipedia)

Today there are still three categories, called Domains, but they all refer to types of cells. The only familiar name is Bacteria. Plants and animals are now small dots in the huge Domain of Eukaryotes (you-CARRY-oats), meaning cells with a nucleus.

The third Domain is the Archaea. Archaea are like Bacteria in that they have no nucleus and are simpler, smaller and older than Eukaryotes. I’ve known so little about Archaea that I wasn’t sure how to say the word. Either AR-kee-ah or ar-KY-a is acceptable. That noun is plural; the singular is AR-kee-on, an Archaeon, sounding faintly of Star Wars.

So how are these Archaea so different from Bacteria that they get their own subdivision of living things? Biologist Carl Woese in 1977 argued they are indeed a different form of life. He showed that in much of their chemical make-up and their genetic sequencing, Archaea not only are distinct from Bacteria but are in some ways closer relatives than Bacteria to the Eukaryotic cells that form plants and animals.

I’ll describe a few features that Archaea and Bacteria have in common and then some features that are unique to Archaea. The information, from Wikipedia and elsewhere, is quite specialized and my renderings of it are admittedly general and selective.

Both Archaea and Bacteria are small, unstructured, and simple compared to the Eukaryotes that came after them. But one achievement they both share has been to try out nearly every possible chemical or environmental source possible to get their energy. Sunshine, salty water, temperatures ranging from volcanic to polar, even radioactive settings—varieties of Bacteria and especially Archaea have found ways to draw energy from, and live off of, these and many other environments.

Another similarity is that Archaea and Bacteria don’t reproduce sexually; two cells don’t mingle their genes to form a new individual that is slightly different from the parents. Instead, individual cells just multiply themselves by two and then divide to form identical clones. But despite their reproductive sameness, they had—and have—a different trick for switching up their DNA. A Bacterium or Archaeon can pump some of its DNA into another cell. Or a cell can just pick up a bit of DNA floating near it. No merging, no swapping, just fresh ingredients. It’s one reason that antibiotic-resistant bacteria in hospitals can spread their immunity to other bacteria so quickly.

archaea hot springs yellowstone nationa park (earth-chronicles.com)

Archaea at home in a Yellowstone hot spring.       (earth-chronicles.com)

This gene-sharing is called lateral gene transfer, and it has an interesting feature. It doesn’t have to take place between members of the same species. For animals and plants, successful sexual reproduction almost always takes place within one species. But DNA can be transferred from any Bacterium or Archaeon to any other variety in those Domains if the conditions are right. If plants and animals could do that, the mind boggles. You might see squirrels transferring some of their DNA into dandelions. Or vice-versa. Such promiscuity makes it easier, I think, to imagine how Bacteria and Archaea have evolved in so many different kinds and colors in so many different environments.

Despite their similarities, though, Archaea are distinct from Bacteria in notable ways. Archaea were first discovered in extremely hostile environments where Bacteria fear to tread: geysers, intensely salty water, even thermal vents at 251 degrees F, the hottest place any organism has been found living. Another feature is that, while some varieties of both Archaea and Bacteria get their energy from light, Archaea do it their own way, through a process unrelated to the photosynthesis that Bacteria passed on to plants. Importantly, too, only Archaea produce methane, essential to organic decomposition. Finally, while many Bacteria can make us sick—think Lyme, Cholera, Syphilis—Archaea may be nicer; no pathogenic Archaea have been discovered, so far.

Archaea and Bacteria had the Earth to themselves for well over a billion years. Then about 2 billion years ago, Eukaryotes appeared, evolving from their single-celled predecessors but larger and internally more developed. By then, Archaea, like Bacteria, had carried out much of the groundwork for living, pioneering what it takes to survive in different conditions, experimenting with energy sources, trying out each other’s genetic parts.

And they succeeded. They didn’t fade away after the sophisticated Eukaryotes began evolving into countless large species. Today, the total mass of Archaea and Bacteria on earth is at least equal to the mass of all the plants, animals and other organisms together. They got the basics right.