For three billion years, life on Earth consisted of single celled organisms. That was so soon after the planet cooled, it leads some scientists to believe life may be common in the universe. Then 800 million years ago, multicellular life burst on the scene and rapidly evolved. Since it took so long to make the multicellular leap, some scientists believe this sort of advanced life may be rare.
Individual cells started grouping up. They collaborated, differentiated, grew in size and ability. Some sacrificed themselves for the good of the many. Compared to the long, dull years of single-celled living, the resulting diversification barely took any time at all. Before long the world was full of trilobites and anenomes, then fish, ferns, pterodactyls, tyrannosaurs, bees, whales, cacti, kangaroos, not to mention us.
Biology: why did life change? How?
A single gene, called RB, studied in a sixteen-cell species of green algae may explain cells banding together into more complex creatures – and may also explain why some cancers grow in us today. Thanks to mutations in the gene, RB can cause cells to clump together into altruistic colonies, or cells in us to selfishly run wild.
Ironically, cancer may be the price we pay for existing at all.
But complex life needed more than variations of RB to evolve.
Physics: life needed Earth to change
RB may have launched complex creatures more than once before our ancestors lasted long enough to evolve.
Scientists think that until 500 million years ago, life on Earth fell victim to high-energy blasts from the sun, [the early sun produced a lot more cell-killing gamma, ultraviolet and x-rays than it does today.] The atmosphere then was too thin to fully protect our single-celled ancestors, whose DNA would have been damaged by such powerful rays. That kept them from becoming more complex.
As the early Earth cooled, heavy metals sunk to the center. Still very hot but now under extreme pressure, the inner core solidified and spun inside the still-molten outer core.
Bingo! A strong magnetic field was generated, deflecting radiation and protecting the atmosphere from being stripped away. Combined with an aging, more-sedate sun, cells were no longer regularly smashed back to their simplest forms.
The details are hard to pin down and studies will continue. “The origin of life remains one of most challenging themes in science.” And, I might add, one of the most fascinating.
Poor dead Mars
The failure to form a proper dynamo of solid inner core and molten outer core may help explain why Mars lost its early atmosphere and has essentially no magnetic field. Perhaps the planet was just too small to manage the trick – Mars is only half the diameter of Earth. The combination makes Mars a hostile planet for life. Whether life ever started there is unknown, and the chance life persists if it did once gain a toehold is unlikely, but NASA and others are working to find out.
Colonize Mars with scifi
The combination also makes Mars a difficult place for us to consider colonizing, but from NASA to Mars One, people are ready to go. For now, you can only travel to Mars in your imagination – or in mine! Check out my scifi On Mars series at Amazon or your favorite on-line retailer. Tragedy and despair follow the first colonists to Mars, but exploration, optimism, and love await them too. With a clue to survival from a cat! Read today. Or, as we say on Mars, tosol.