Life Started Earlier Than Expected
Back in November 2020, when the pandemic was in full swing and we were all staying home, I started thinking about creating my own newsletter.
On December 5th, 2020, I officially launched it with just 5 subscribers (my family and friends, of course). The first newsletter came the next day, and it was about evolution. But I made one big mistake in it: I said that ‘Life started 4 billion years ago.’
That estimate is now outdated. A recent study shows that life likely began around 4.2 billion years ago. But what’s the significance of this discovery?
This drawing is representational, not real.
Light blue line = Life was predicted to have started in this period until recently.
Dark blue line = Life is now predicted to have started in this period.
Why does this discovery matter?
It’s important because it helps us understand the conditions needed for life. This knowledge could eventually help us find life on other planets, like Venus, Mars, and some exoplanets.
This drawing is representational, not real.
But how did scientists figure this out? Was this just a lucky guess?
How do we know it’s true?
First, we need to talk about LUCA, or the Last Universal Common Ancestor (and no, it’s not the Disney movie😆). LUCA is the predicted organism from which all life on Earth evolved.
The simple answer is that researchers used DNA and evolutionary data to determine when LUCA lived.
Note: The process I’m explaining here is simplified. There were many complexities involved, including mathematical models and complex software.
Here’s a brief overview of how they did it: Scientists looked at DNA, which exists in all living things. Before LUCA appeared, the DNA duplicated and performed the same functions in early organisms.
Over time, this DNA mutated, creating the genes we have today. These mutations are a natural part of evolution. By studying these changes, researchers built something called a phylogenetic tree, which shows the relationships between species over time.
A phylogenetic tree is a way to visualize evolutionary similarities.
Next, scientists calculated how often these mutations occurred and used this information to work backward through the tree to estimate when life began. They also compared this data to fossils, but that’s a whole other topic for another time.
Using these methods, researchers concluded that life likely started 4.2 billion years ago. They also discovered that LUCA had a genome size of 2.49–2.99 megabases (Mb), which is bigger than the genome of strep throat bacteria (1.8–2.3 Mb).
The most fascinating thing, though, is that scientists identified some of LUCA’s DNA. So, we can learn more about what made LUCA so special. Since this is getting a bit long, I’ll cover that in the next newsletter.
In the meantime, subscribe to get access to the newsletter!