In the Cosmic Calendar, the Origin of Life falls somewhere around now.* About three and a half billion years ago, the great abundance of life on Earth began, probably with a single replicating molecule – a precursor to DNA. Every living organism today, from the tiniest bacterium to the largest whale, descends in an unbroken line from that tiny bundle of atoms.
Today, I invite you to consider this:
We still reproduce as single-celled organisms.
Every act of human reproduction involves one cell from each parent. A single cell. For all our wondrous complexity, our bountiful organs and tissues, our towering intellects and tender thoughts … for all that, we still have to humble ourselves to the level of our distant, millions-of-generations-past ancestors in order to participate in that most ancient, most definitive act of life: reproduction.**
* In fact, the details of this event, including its exact date, are difficult to pin down. The Wikipedia article on abiogenesis gives possible dates ranging from 4.2 billion years ago (bya) to 2.4 bya – that is, 11 September to 29 October. However, today falls somewhere in the middle of the range, just over 3.5 bya. The fact that 28 September is also my daughter’s birthday makes me even more prone to contemplating life’s origins today.
** Not all multi-cellular organisms are so constrained. Many plants do a significant part of their reproduction by sending out shoots or otherwise cloning themselves, rather than going through the whole one-cell business. Who’s superior now, eh?