Simple to complex: that’s been the essence of evolutionary theory ever since Charles Darwin imagined some organic molecules coming together in a warm little pond eons ago. Whatever simple life form emerged from his pond started his evolutionary process that led to the human brain. But what if the “last universal common ancestor” was already highly complex? What if bacteria and archaea are “devolved” remnants of a more complex ancestor? That’s exactly what a new study is claiming.
“Last universal common ancestor [LUCA] more complex than previously thought” is the headline on PhysOrg. Here’s what’s out: “Many believe LUCA was little more than a crude assemblage of molecular parts, a chemical soup out of which evolution gradually constructed more complex forms. Some scientists still debate whether it was even a cell.” Not according to a study from the University of Illinois at Urbana-Champaign: “New evidence suggests that LUCA was a sophisticated organism after all, with a complex structure recognizable as a cell, researchers report.”
The article goes on to describe discovery of an enzyme common to all three kingdoms of microbes. This enzyme, vacuolar proton pyrophosphatase, has been found in prokaryotic bacteria, along with a structure that is “physically, chemically and functionally the same as an organelle called an acidocalcisome” that is common in eukaryotic cells. Acidocalcisomes are complex organelles that help control osmosis. They contain protein pumps and gates that actively transport water, calcium, and ions. An analogous structure and enzyme is also present in archaea. Conclusion: the “last universal common ancestor” (LUCA) was already complex enough to contain these organelles, along with their molecular machines, and therefore “may have been more complex even than the simplest organisms alive today,” according to James Whitfield, a co-author of the study published in Biology Direct….
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