A new commentary has once again dismissed the COVID-19 lab leak theory by applying a classic evolutionary theory to elaborate why SARS-CoV-2, the virus responsible for COVID-19, could only come from nature.

The insight piece, titled "On the origin of SARS-CoV-2 – The blind watchmaker argument," was published on the academic journal Science China Life Sciences on Friday by 22 scientists working in Chinese universities and research institutions.

The argument the authors applied stated that natural selection is a blind, unconscious, automatic process which has no purpose in mind and plays the role as a blind watchmaker.

A perfectly adapted species could not be created at once, but would have to accumulate small, adaptiveness-enhancing changes through random mutations over long periods of time, reported Xinhua citing Wu Chung-I, corresponding author of the commentary and professor of the School of Life Sciences at Sun Yat-sen University in south China's Guangdong Province.

SARS-CoV-2 is "extremely well adapted to the human populations and its adaptive shift from the animal host to humans must have been even more extensive," said the commentary, which, according to the blind watchmaker argument, "can only happen prior to the onset of the current pandemic and with the aid of step-by-step selection."

"In this view, SARS-CoV-2 could not have possibly evolved in an animal market in a big city and even less likely in a laboratory," it added.

The article also said that researchers have successfully selected SARS-CoV-2 strains that can infect mice, which are otherwise resistant to the infection. However, "the enabling mutations account for such a tiny fraction of mutations that an efficient screening of mutations by natural selection is required."

The authors inferred that before the onset of the COVID-19 pandemic, the virus may have experienced some forms of multi-step evolution in human populations, leading to its extraordinary adaptiveness.

They said the claim of non-natural origin of SARS-CoV-2 is "moot," as no known natural law "prohibits the SARS-CoV-2 genome to evolve to its current state." They called for focus on the natural processes in relation to the virus' origin, which would be "more productive."

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