The moment when life ceased to be microscopic

The moment when life ceased to be microscopic

Photo by Magda Ehlers from Pexels

Originally published 26 October 1998

Ear­ly in Jules Vernes’ 20,000 Leagues Under the Sea, Cap­tain Nemo wel­comes Pierre Aron­nax, pro­fes­sor of nat­ur­al his­to­ry at the Paris Muse­um, aboard his submarine.

You have pur­sued your stud­ies as far as ter­res­tri­al sci­ence can go,” Nemo tells the pro­fes­sor. “But you don’t know all because you haven’t seen all.”

He promis­es Aron­nax excite­ment aboard the Nau­tilus: “You are going to tour a land of mar­vels. Aston­ish­ment, amaze­ment will become your every­day state of mind… Start­ing today, you’ll enter a new ele­ment, and you will see what nobody has seen before.”

And so begins an epic voy­age into the depths of the sea, an alien realm where every­thing sways and slith­ers with the gen­tle tug of tide and cur­rent. A world of inky dark­ness, where crea­tures depend for food on the decay­ing organ­ic mat­ter that rains down from the sun­lit world above.

I shared some­thing of Aron­nax’s under­sea adven­ture when I watched a video made by the Mon­terey Bay Aquar­i­um Research Insti­tute. It was a com­pi­la­tion, set to music, of mag­i­cal sights from the hid­den world of 200 fath­oms, pho­tographed by the insti­tute’s remote-con­trolled sub­ma­rine ves­sels, under the direc­tion of Bruce Robison.

These robot­ic craft slip and glide qui­et­ly in the dark abyss with the grace and agili­ty of human divers. And they can go where no human could sur­vive with­out the awk­ward pro­tec­tion of heavy steel and glass.

What won­ders they reveal! An alciopid worm that writhes like an ani­mat­ed sin­gle-strand bowl of spaghet­ti. A sergestid shrimp that cruis­es a jet black “sky,” feet pro­pel­ler­ing, long anten­nae stream­ing like con­trails. An ethe­re­al-blue loli­go squid that soars like a air­borne orchid.

But the most won­der­ful denizens of the deep are the jel­ly­fish, ghost­ly and gelati­nous, some of them glow­ing with mys­te­ri­ous lights.

I remem­bered the words of Pro­fes­sor Aron­nax, who watched jel­ly­fish as he walked with Nemo in his abyssal gar­dens: “Some of them were shaped like a smooth semi­spher­ic umbrel­la, with red and brown stripes and a fringe of 12 sym­met­ri­cal ten­ta­cles. Oth­ers looked like over­turned bas­kets from which there trailed wide leaves and long red twigs. They swam with quiv­er­ings of their four leaf-like arms, let­ting the rich tress­es of their ten­ta­cles float in the water.”

The jel­lies seem as much a part of their medi­um as clouds are part of the sky, as if there is in water itself a ten­den­cy to thick­en and to flower. They undu­late their spec­tral bells and wings like vis­i­tors from a world of pure spirit.

They are, in fact, most­ly water, with about the same per­cent­age of sol­id mat­ter as Kool-Aid. They have no blood, heart, bones, or brain, nor any­thing like real image-form­ing eyes. Their gelati­nous bod­ies have a sin­gle ori­fice, which serves for the intake or dis­charge of nutri­ents, waste, and repro­duc­tive cells.

I would have liked to pre­serve a few spec­i­mens of these del­i­cate zoophytes,” says Aron­nax, “but they are clouds, shad­ows, illu­sions that dis­solve, melt, or evap­o­rate after they are removed from their native element.”

With­out back­bones, shells, or rigid parts of any kind, they are one with their watery uni­verse, made ani­mate by the mag­ic of life.

Jel­ly­fish are among the ear­li­est mul­ti­celled crea­tures found in the fos­sil record. They are a sig­nif­i­cant part of what is called the Edi­acara fau­na, after the Edi­acara Hills of South Aus­tralia, where a fine-grained, hard, sandy rock has beau­ti­ful­ly pre­served a record of life in the sea more than 650 mil­lion years ago.

This was the moment in Earth­’s his­to­ry when micro­scop­ic blobs of amoe­bic pro­to­plasm, which had lived on their own for 3 bil­lion years, began to com­bine into mul­ti­celled organ­isms, meld­ing their respec­tive tal­ents for the com­mon good.

Some cells spe­cial­ized to build body walls, oth­ers to make the “jel­ly” between the walls, oth­ers to make ten­ta­cles, oth­ers to sting, oth­ers to digest. This divi­sion of labor is the cen­tral sto­ry of all macro­scop­ic life dur­ing the past 650 mil­lion years, and jel­ly­fish were among the first to get on with it.

What beau­ty of form fol­lowed from func­tion! With spe­cial­iza­tion and col­lec­tiviza­tion, life emerged from pro­to­plas­mic amor­phous­ness into shape, col­or, sym­me­try, and extrav­a­gant design. The video images of jel­ly­fish bal­leri­nas flut­ter­ing their tutus, or adrift like Mont­golfi­er bal­loons, give us a glimpse of that moment in geo­log­ic his­to­ry when life ceased to be microscopic.

How did it hap­pen? What caused our micro­bial ances­tors to forego their indi­vid­ual exis­tences and embark upon a life of col­lec­tive adven­ture? We do not know.

We don’t know all because we haven’t seen all, as Nemo says.

Which is why sci­en­tists at places like the Mon­terey Bay Aquar­i­um Research Insti­tute con­tin­ue to explore the deep sea, and why geol­o­gists tramp the Earth seek­ing an ever-more-detailed fos­sil record. They are piec­ing togeth­er a sto­ry whose last chap­ter is the present exhil­a­rat­ing diver­si­ty of life.

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