When we speak of genealogy, we are usually thinking of parents and grandparents, and perhaps we also feel a mysterious connection to tales about our ancestors in more ancient times. It’s not an exact science, but we can begin to see that many of our traits and behaviours are inherited, and not unique to us.
The Dawn Of Life Preview Exhibit at the ROM gives us the opportunity to see a 500-million-year horizon – a mind-boggling exploration! Suddenly, our genealogy project seems very daunting. What do these strange, wriggly things have to do with us???
Here’s what I’ve come up with so far: Biologists tell us that the first living organisms appeared on the Earth about four billion years ago and began to evolve very slowly. Organisms normally inherited their physical characteristics from their parents, but when mutations occurred, new characteristics, and ultimately new species, arose. At a certain point (we can’t say exactly when,) organisms appeared that contained all the basic genetic material found in organisms today. In other words, all living things can be traced back to a single lifeform – to a universal common ancestor (UCA).
Biologists consider the “gene” to be the molecular unit of heredity. They describe a genetic “code,” or set of rules, that govern biological evolution. They classify and organize all lifeforms in a hierarchical chart, based on differences in their genetic code. When life is modeled in this way, it creates a branching, tree-like pattern called a phylogeny. The UCA is at the root of the tree, and all the current species are like leaves on the tips of branches.
A Poster in the Biodiversity Gallery provides a good summary:
This [phylogenic] tree depicts major life forms, based on their evolutionary relationships. The earliest life forms lived four billion years ago. If each species living today were represented by a leaf, there would be more than two million leaves. Only one would represent humans.
Hmmm…This line of thought is a helpful foundation perhaps, but does it really explain who we ARE, and where we COME from? I think I need to work with this a bit more…
(Thanks to Michael Foisey for his helpful comments on my original text.)