Life on Earth Evolved From an Ingredient in Fake Lemon Juice, Says New Study

Monday, 08 January 2018 - 10:54AM
Monday, 08 January 2018 - 10:54AM
Life on Earth Evolved From an Ingredient in Fake Lemon Juice, Says New Study
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Image credit: Pixabay
One of the biggest mysteries about life on planet Earth is what catalyst kicked everything off.

We know that life exists now. We know that it didn't exist in the distant past. Scientists are having a really hard time figuring out what happened way back at the dawn of time to create this wholly unique phenomenon in the first place.

Experts have created all kinds of theories to try to explain where life came from. Some suspect that the first single-celled organisms were born from the arrival of a large, fertile meteor. Others believe somewhat more outlandish theories about alien caretakers or polluters chucking life down onto our world, leading eventually to the existence of our species.

Now, there's a new theory, and it has to do with one of the major chemicals found in lemon juice.

Believe it or not, citric acid is a vital part of all aerobic organisms. You might not be a fan of sucking lemons, but your body cycles citric acid through itself in order to perform even basic motor functions—this acid is key to the process of burning oxygen in order to fuel your muscles.

According to a new paper published in Nature Communications, the first life forms on this planet probably also relied on a variation on the citric acid cycle in order to move around.

You may have noticed the major problem with this logic: without organic life on Earth, there could be no citric acid—the compound is an organic creation to begin with. There was no fruit on Earth before the creation of the amoeba.

This is part of the reason why life might be so rare across the known universe. According to the new paper, early life forms may instead have relied on 4-hydroxy-2-ketoglutarate (HKG) and malonate to provide a similar catalyst to enable movement.

Essentially, with these two inorganic compounds present when life first began, early cells would have used them in a similar manner to the way that our bodies cycle through citric acid in order to grow and develop.

According to the paper's lead author, Ramanarayanan Krishnamurthy:

Opening quote
"The chemistry could have stayed the same over time, it was just the nature of the molecules that changed. The molecules evolved to be more complicated over time based on what biology needed."
Closing quote

This still doesn't explain a lot of things, such as the impetus that created the first single-celled organism to kick off this planet's inhabitants' family tree.

The theory does, though, help us to understand the conditions that are required for early life a little better. We can now theorize as to how these early creatures were able to survive in the absence of more advanced organic acids that more modern creatures use to function.

This has implications for our search for life beyond our planet, as well. As much as we might wish to find bug-eyed aliens on Mars, or even further afield, if the presence of HKG and malonate are required in order for a planet to be able to sustain some form of early organic life, we may find that the specific conditions on our world are even more unique and rare than we'd previously assumed.

If so, it would explain why so many of our attempts to find aliens have proven hopeless, and it could help us to narrow down the search as we look specifically for the planets that have these key building blocks of life, in order to locate worlds that could house new alien friends for us to share recipes with.

In the meantime, we may have solved one of the big questions about how life originally formed on this planet. What came first, the chicken or the egg? Apparently, these were both, in fact, preceded by artificial lemon juice.
Science News