dhw's obsession with 'humans plus food'; current studies (Introduction)

by David Turell , Monday, October 30, 2023, 18:48 (390 days ago) @ David Turell

There are more cells on Earth than stars:

https://www.science.org/content/article/new-calculations-say-there-are-more-living-cell...

From bacteria to blue whales, the number of cells in living things exceeds the estimated number of sand grains on Earth by a factor of a trillion. It’s 1 million times larger than all the stars in the universe. And the number of cells that have ever lived is 10 orders of magnitude larger still, according to new estimates researchers reported last week in Current Biology.

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Peter Crockford, a geologist at Carleton University, and his colleagues began their inventory by combining existing estimates of the number of microbes currently in the ocean, soil, and Earth’s subsurface with the number of cells in larger organisms. The result was the number of cells alive today. That number—an eye-popping 10^30 cells, the majority of them cyanobacteria—was the starting point for calculating the total number of cells that have ever lived.

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The key to that calculation was primary productivity, the conversion of carbon dioxide (CO2) into the carbon-based compounds that fuel all of life. Those compounds—sugars and starches for example—move up the food chain: Plants and photosynthesizing microbes are eaten by other organisms, which in turn are eaten by even bigger organisms. All of these die and are consumed and broken down by insects and microbes. Those consumers return CO2 to the atmosphere as they breathe and die, completing the carbon cycle. (my bold)

To understand how primary productivity has changed over Earth’s geologic history, Crockford and colleagues combed the scientific literature for estimates of the numbers and types of photosynthesizing organisms at different points in time and how much “food” they produced. Knowing the primary productivity of modern cells, the researchers then were able to wind the clock back to calculate how many cells would have been required to sustain past levels of productivity. They adjusted the calculation based on factors such as when different lifeforms evolved and how ice ages dampened the activity of those organisms. (my bold)

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Putting all the math together, somewhere between 1039 and 1040 cells have ever lived. Together, those photosynthesizers have cycled through all of Earth’s carbon about 100 times. And the researchers’ calculations suggest these numbers are approaching an upper limit. Earth simply doesn’t have the resources to support more than 10^41 cells, they say.

Comment: note the emphasis on food. Note my bolds. Life can't live without it. So, it is not just human food, but everyone's to dhw's surprise.