Monday, February 13, 2023

Burrowing Things


Burrowing Owl at Cesar Chavez Park, February 2011

The oldest form of life on Earth has survived all the great extinction events and is an important part of not just "the ecosystem," but even of the internal microbiome of the likes of owls and humans. Bacteria have ruled the planet for around 3.5 billion years, and all us plants, fungi, and animals had to emerge and evolve in their royal presence. "[T]he cell biology and genomes of all modern eukaryotes were built on a bacterial foundation."

An evolution in bacteria was responsible for the Earth's first great extinction event, which doesn't even count in the so-called five great extinctions, and which made life possible for us eukaryotes. Interestingly, the five extinctions that do count were all a result of rapid climate changes that involved either planetary cooling or warming. 

The earliest of the big five occurred 444 million years ago. But that first pre-big-5 extinction occurred around 2.5 billion years ago and is known as the Great Oxidation Event. It was brought on by the proliferation of photosynthesizing cyanobacteria that produced a deadly gas: oxygen. The bacteria that had been basking blissfully in a warm methane atmosphere for a billion years were unceremoniously torched by this new, highly reactive gas.

As I was thinking about all this it occurred to me that our own ancestral gut microbiomes, most of which are composed of obligate anaerobic bacteria, are pretty good sanctuaries from inflammatory oxygen. Somehow the anaerobes that survived the deadly new Oxygen World burrowed into whatever new forms of life came along that could take advantage of oxygen's power. Now here we are, with each milliliter of our large intestines providing a home to 100 billion microbes of perhaps 400 species.

All us animals, including birds, live with symbiotic microorganisms in our guts, where the tiny critters provide "a multitude of nutritional, defensive, and developmental functions with a myriad of implications for host health and fitness." 

We are dependent on minerals and gases, on liquid water, on microorganisms, and on the plants and animals we consume to power our lives. If you think about it, we truly are one with everything. 

Owl on the Shoreline

Owl in the Spotlight

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