Adventures in Everyday

What? Multiple Origins of Life?
March 19, 2008, 2:16 pm
Filed under: biology, science

Questions I want answered about the origin of life:

  • Why is “the origin of life” usually described only as a singular event?
  • Why must we assume that once life on Earth appeared, it was invincible and never went extinct?

Deep sea vents

For the last several years, scientists have gradually become cozier with the idea that life on Earth first originated near deep sea hydrothermal vents. It’s an interesting concept too, because the primary producers in these areas don’t use photosynthesis at all (how could they – it’s pitch black down there). Rather, primary producers, such as the giant blood-red tube worms more than 2 meters in length (taking well over 100 years or more to grow), house symbiotic chemoautotrophic bacteria that function analogously to chloroplasts in plants.

→ Watch a great National Geographic video about hydrothermal vents here

But if these deep sea vents have been around for many billions of years, and if the general scientific consensus is that abiogenesis occurred as early as 4.4 billion years ago, why do we think that life could have emerged only once?

Many origins, and many extinctions

Deep sea vents are found all throughout mid-oceanic ridges. Accordingly, life should have been equally likely to have originated at any one vent (or, more likely, any group of vents). Some of these sites must have been at least somewhat isolated from other sites, and so any abrupt geological activity could have heartlessly wiped out everything.

Perhaps dozens or hundreds of relatively unique proto-life forms originated all over the planet many times – and were subsequently squelched by random environmental changes (as is Earth’s way, it seems).

And, finally, maybe it was just one variety, or proto-kingdom, of pre-life that evolved far enough to out-compete every other form of life.

Extraterrestrial life in our solar system?

Europa is one of Saturn’s many moons. Europa is of special interest, however, because of the thick layer of ice (10 – 30 km) covering its surface and the estimated 100km deep liquid ocean underneath. Sure, the surface of the moon is a balmy −160°C at the equator, but what if Europa, like Earth, has undersea hydrothermal vents?

Extraterrestrial life might exist in Europa’s deep ocean. But if it has evolved around hydrothermal vents, could it have evolved in multiple locations and at multiple times throughout its history, as I have hypothesized above for Earth’s ancient past? Maybe. However, because Europa is so thought-numbingly cold, perhaps life forms or proto-life forms that existed at one hydrothermal site could have never spread to other sites.

Unfortunately? Maybe. Or maybe it means that if there is any life at all on Europa, there may be dozens or hundreds or more unique, isolated forms of extraterrestrial life.

On the other hand, isolated life is more likely to become extinct, and we may find nothing but ancient fossils (which would still be fascinating).


2 Comments so far
Leave a comment

the best post yet. I love links to national geographic videos.

Comment by kristyn

good questions. We talked about that. Why doesn’t anyone else wonder those same things? Maybe I just don’t hear about it.

Comment by Jen

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