He that sitteth in the heavens shall laugh: the Lord shall have them in derision.
Psalm 2:4
"Here’s the scoop: a complex reaction essential to life on earth has
never been replicated by engineers, but it “emerged” in bacteria
somehow, and has not evolved since.
Q: Does that sound like Darwinian
evolution?
Nitrogenase is a true wonder of nature. This enzyme, found in 
certain
bacteria, is able to break the tough triple bonds in atmospheric
nitrogen (N2), allowing plants to utilize the essential
element found in every protein.
Human engineers, eager to fix nitrogen
for fertilizers, have to use a very energy-intensive process at high
temperatures and pressures to break those bonds (the Haber-Bosch
Process), but the bacteria do it easily at room temperature.
Q: How did
this near-miraculous feat “emerge” in the world’s so-called simplest
organisms, and why hasn’t it evolved? Therein lies a tale. It’s told in a
preprint that appeared this month.
Nitrogenase resurrection and the evolution of a singular enzymatic mechanism (bioRxiv,
5 Feb 2023). Researchers at the University of Wisconsin and Utah State
decided to look into the evolution of nitrogenase enzymes. When did they
first appear? Is there an evolutionary sequence from a common ancestor?
Here’s what they found, contradicting their assumptions about
evolutionary “emergence” and
The planetary biosphere is powered by a suite of key metabolic innovations that emerged early in the history of life. However, it is unknown whether life has always followed the same set of strategies for performing these critical tasks. Today, microbes access atmospheric sources of bioessential nitrogen through the activities of just one family of enzymes, nitrogenases. Here, we show that the only dinitrogen reduction mechanism known to date is an ancient feature conserved [i.e., unevolved] from nitrogenase ancestors.
For their experiments, they used engineering (a form of intelligent
design). They engineered what they consider an “ancestral” form of the
enzyme and inserted it into a living bacterium. If evolution were true,
there should have been so many changes over billions of years that it
would seem unlikely to work at all.....none of their explanation bears on how nitrogenase first appeared.
They’re saying that however it “emerged,” nitrogenase was “constrained” from evolving because it had too important a job to do. So after some unexplained “emergence” (a virtual miracle without plan or foresight), it did not evolve further.Our results suggest that life may have been constrained in its sampling of protein sequence space to catalyze one of the most energetically challenging biochemical reactions in nature. The experimental framework established here is essential for probing how nitrogenase functionality has been shaped within a dynamic, cellular context to sustain a globally consequential metabolism.
Q: But what is this “protein sequence space” they speak of?
A: It’s like a game of chance." CEH
