Tag Archives: origin of life

Shaped droplets, diatoms and the origin of life

A remarkable paper appeared online 09 December 2015:

The authors, materials scientists from Bulgaria and the UK, mused out loud that their discovery that cooled oil droplets become polygonal had something to do with the morphogenesis of living creatures, but didn’t know which ones. I immediately started writing “On polygonal drops and centric diatoms” followed shortly by “The tensegrity origin of life via shaped droplets as protocells”, and some of the authors of “Self-shaping of oil droplets” are joining us as co-authors.

I had long been puzzling over the uncanny, nearly perfect symmetry of some centric diatoms, which I demonstrated by rotating a digital image of a diatom with n sectors by 360/n degrees and subtracting the images, in:

  • Sterrenburg, F.A.S., R. Gordon, M.A. Tiffany & S.S. Nagy (2007). Diatoms: living in a constructal environment. In: Algae and Cyanobacteria in Extreme Environments. Series: Cellular Origin, Life in Extreme Habitats and Astrobiology, Vol. 11. Ed.: J. Seckbach. Dordrecht, The Netherlands, Springer: 141-172.

Here’s a less perfect example than those used in that paper, the diatom Triceratium favus with n = 3, so the rotation is 360/3 = 120o (with kind permission of Stephen S. Nagy of Montana Diatoms):

 

The subtraction image on the right is black where the match is best. The two published examples, with n = 5 and 11, came out almost totally black. You can try this yourself with any front-on image of a diatom you can find on the Internet, if you have software that allows rotation by any angle. For example, try Word: Format Picture: Size: Rotate and scale, after trimming the picture so that the center of the diatom is in the center of the image. I’d like to see what you get. Please send the original, rotated and difference images to me at: DickGordonCan@gmail.com, along with the exact source of the diatom image. Anyone mathematically inclined (and these diatoms instantiate a rotation group) may wish to write a computer program to quantify the degree of symmetry by coding some of the math in:

We in polar climes are all aware of the beautiful, generally hexagonal symmetry of snowflakes, which has it explanation in the crystalline stacking of water molecules in ice. Some can approach triangular, although they are hexagons with edges of different lengths:

Libbrecht2016 triangular.jpg

This is from:

Libbrecht, K.G. (2016). Guide to Snowflakes: Triangular Crystals.

with kind permission of Kenneth G. Libbrecht. More pointy triangular snowflakes may be seen at:

Bentley, W.A. & W.J. Humphreys (1931). Snow Crystals,  McGraw-Hill. (reprinted by Dover Press in 2003).

But diatom shells are not crystalline at all. They are made of amorphous silica, which at higher temperatures would be molten glass. They are frozen in the glassy state. Are diatoms real life cases of the liquid metal robot T-1000 in the movie Terminator 2? That puzzle is why diatom symmetry is uncanny.

So we start the New Year with a newly discovered phenomenon: oil drops that “should” be mere spherical blobs looking like diatoms. I’ll just show one oil triangle here (with permission of Nature Publishing Group), though the polygons go up to 11 sides:

 

Denkov&2015 Fig2b triangle.jpg

How can a liquid have sharp points like that?

Connections rattled in my brain. Denkov et al. suggest that the oil molecules line up at the perimeter, forming plastic-like bundles as cooling proceeds. Those bundles could be stiff, and prevent the drop from curving due to its surface tension. But then stiff rods confined by tension means that shaped droplets are tensegrity structures. But this is precisely what Steve Levin and I were complaining about the presentations at the origin of life conference we attended together last November: protocells, the blobs that supposedly led to life, had no postulated structure. Two problems solved at once! Diatoms and protocells are and might have been tensegrity shaped droplets. Martin Hanczyc’s oil droplet protocells might be polygonal under some conditions, and Vadim Annekov’s molecular dynamics simulations of diatom shell morphogenesis interacting with cytokeleton (in progress) may be enhanced. Not quite as good as the kids’ book “Seven in One Blow“, but a very satisfying pair of results.

And by the way, this is why theoretical biologists should be regarded as highly as theoretical physicists, although in general we don’t get no respect.

Could there have been a single origin of life in a big bang universe?

Abell 2218 HST WFPC2 I, V, B

Hubble Telescope Image, one of the best ever views of the massive galaxy cluster Abell

Excerpt from our book Embryogenesis Explained:

We define embryogenesis as the ability to produce the right kind of new cell, in the right place at the right time. This phrase “the right cell, in the right place, at the right time” is an expression due to Hans Driesch around 1890. All other aspects of embryology like morphogenesis, differentiation, and regeneration arise from embryogenesis of a first simplest proto-life form. Where and how did this first life originate?

There is a delightful scene from the Star Trek Next Generation television series where a powerful, immortal being, Q, takes Captain Jean Luc Picard back in time and space to stand looking down at a tiny pool on a hostile volcanic planet. Q tells Picard this is Earth eons ago and Picard should look in the pool. Q then laughs. Q says that THE miracle is about to occur. Right there in that puddle, Picard’s far distant first ancestor is about to come into existence. Q comments that humans are the mere product of a pond of goo. In their ongoing debate about the merit of humans Picard quotes Shakespeare saying:

“I know Hamlet. And what he might say with irony I say with conviction. ‘What a piece of work is man! How noble in reason! How infinite in faculty! In form, in moving, how express and admirable. In action, how like an angel. In apprehension, how like a god…’”.

Our God-like form is assumed to have begun in a primordial soup from some primitive bit of RNA (or proteins) that was able to self-replicate. There are many hypotheses about the conditions that allowed first life to form and attempts to simulate the event by chemistry or computer. The two most common are that this remarkable feat was accomplished while inside the simplest of membranes in a pool of water or near a hot hydrothermal vent.

Our universe started with the Big Bang 13.75 billion years ago. It started hot and cooled down, forming galaxies and stars and perhaps planets as early as 200 million years after the Big Bang. Our records of life on Earth begin a mere 3.8 billion years ago with what looks like prokaryotes in fossils and the unique chemical signatures of life. While prokaryotes are simple compared to us, they are organisms that have evolved to levels of complexity far beyond the proto-life forms scientists envision at the origin of life. So where did life begin? Did first life start here on Earth at some time before 3.8 billion years? Did it begin somewhere else and then transported here? As mankind gets ready to travel beyond our moon this is becoming a more urgent question and more hypotheses have been brought forward to try to answer it.

If life started elsewhere in our turbulent Milky Way galaxy and traveled to Earth, this increases the possible environments that life may have started in. It also increases the time total available for life to have evolved to form those first recorded prokaryotes. If life formed on earth then the maximum time is sometime after the 4.8 billion years since Earth started. If life started elsewhere and traveled here, then the time is stretched to a maximum of about 13.55 billion years ago. We eukaryotes are far more complex than our prokaryotic ancestors. Humanity arose from our prokaryotic ancestors in a mere 3.8 billion years. This means, if life began beyond Earth, then complex intelligent beings like us could have arisen in our universe as soon as 9 billion years ago, well before Earth even formed.

Maybe life on Earth started with nothing more complicated than prokaryotes because it took 9 billion years for life to evolve that far. Extrapolated data suggests this might have been the case. If that idea holds up, then life indeed did not originate on earth but life did find the right conditions for the first evolution of complexity beyond prokaryotes to produce us here on this obscure little blue planet. In our own galaxy there may be 15 to 30 billion habitable planets and even more exomoons that are habitable. If that is true then the prokaryotes that arrived here on Earth may have also been deposited on other suitable planets as well and may have been evolving along at the same pace as us. Perhaps we are not alone and all complex life like us is approximately the same age as we are.

The universe is expanding much faster than primitive life could have travelled about in space, borne on the winds of supernovae explosions, hypervelocity stars, galactic ejecta, or transferred during frequent galaxy collisions. Whole “rogue” planets are occasionally ejected from their solar systems and bounced out and sometimes towards capture by other stars like celestial billiard balls. Taking into account all of these phenomena, we can estimate that the “speed of life” without technological assistance is limited to 1000 kilometers per second. This is 1/300th of the speed of light, which is 300,000 kilometers per second (299.792458 kilometers per second in vacuum, to be more precise). Despite the vast distances in space, there are many means for life to get around, even between galaxies. But life can only get so far.

Making the generous assumption that life is somewhat evenly distributed across the universe, Dick, writing with Richard Hoover, calculated that life must have started independently at least 50,000 times, if not many more. New results suggest that the speed of life could approach the speed of light, as may happen with stars and their solar systems flung out of colliding galaxies by close encounters with the pair of their black holes, possibly carrying along their inhabited planets. Even then there would still have to have been 170 independent starts to life, to fill our universe.

If we assume first life began here on earth and did not arrive from elsewhere, then the organic molecules required for life to start must be from somewhere. There is more than one hypothesis about that. Perhaps organic molecules were made fresh here on Earth from nothing more than simple gases by fierce activity of lightning and/or volcanoes. Perhaps they were delivered by crashing comets or meteorites on our young planet before it had an atmosphere. Our galaxy is certainly rich in organic molecules we know are synthesized around stars.

The religious among us who nonetheless embrace the overwhelming evidence for evolution often see the finger of God as stirring that primordial goo: yes, life did start out as goo somewhere in the universe, maybe more than once, but it could only have done so because God did it. With 170 to 50,000 plus start ups, we could suggest that He’s still busy doing it. As none of us have a Q to take us back to the very first primordial goo, these questions may never be satisfactorily resolved. The best we can aim for now is a re-creation “from scratch” of something we would call life. And if one must invoke God, then we can at the very least, expect to figure out exactly how He does it.

Finis

Could there have been a single origin of life in a big bang universe? No, unless we accept that only our remote corner of the universe has life. If life exists throughout the universe, as in the vision of Roddenberry’s Star Trek universe, then there must have been multiple origins of life. But we have yet to discover any real evidence that there is life beyond our planet. Stay tuned.

Read about The Speed of Life. The speed of life as postulated in Gordon&Hoover may be an underestimate. We previously reviewed From the First Star to Milkomeda where a star doing a slingshot around two black holes in colliding galaxies could increase the speed of life to near the speed of light, assuming anything on its planets could survive such a ride.