How did the first organism on Earth become “alive”? Scientists have a good guess* as to when life first appeared; sometime between 3.5 and 3.8 billion years ago. That’s all great. We have a rough 300 million year window on when life arose on our planet.
But, how did it happen? Was it like a light switch that was just flipped on? One second this “thing” is not alive then… bam! It’s alive and we’re off to the races. Or, was it a gradual process where it was “almost alive” then “a little more alive” then “even more alive” until it became just “alive”?
Arizona State University’s Dr. Sara Imari Walker, an astrobiologist and theoretical physicist, spends her days pondering this type of question. She applies mathematical models to the emergence of life.
While it seems made up, she says the term “almost alive” is a real term used by scientists. During her ASU Connections appearance on September 7th, Walker says, “It’s in a technical paper. So, it is a scientific term!” She even feels that the “almost alive” stage is one of the missing pieces to discovering how life emerged.
“We know what simple chemical systems look like and we know what complex fully functional cells look like but we’re missing this entire range of these intermediate states. We don’t really know what they look like,” explains Dr. Walker, “Those are the ones that are really important on the pathway from prebiotic chemistry that might have dominated the early Earth to what we know of the earliest cells. And those, I would call ‘almost alive’.”
Questions like this give a tiny glimpse into what life is like for Dr. Walker as she studies the emergence of life. Her work focuses on the transition from complex chemistry to the simplest forms of biology. To make matters even more difficult, she says crossing over the life threshold wouldn’t even be noticeable, “You would never know the exact point you crossed (into being alive). You couldn’t decide the exact point when this new system arose.” It’s like looking for something that upon finding it, you may never know you actually found it. Fun, huh?
The discussion then turns into defining that life-transition. That requires another question be answered; What is the definition of life? That question often leads to another very deep philosophical rabbit hole but Dr. Walker makes it somewhat simple. She says defining life has a lot to do with the way biological systems use information. But even her thoughts on life aren’t set in stone, she says they vary, “on a day-to-day basis.”
Her view on the “almost alive” vs. “gradually alive” argument is also pretty fluid. “I think my answer to that questions depends on the day of the week you ask me,” she joked.
For the record, this time she was asked on a Monday.
*Ask one person, get one answer. Ask another, get another answer. Repeat.
Listen to Dr. Walker describe her research and more by listening to her full ASU Connections appearance from August 31st, 2015.
Photo credit to Abigail Weibel