Photo/Illutration A specialized chemical to detect DNA shows a swarm of cells with DNA that glow green in this image. (Provided by Yohey Suzuki, an associate professor of earth and planetary science at the University of Tokyo)

Scientists detected living microorganisms within a sealed fracture of 2-billion-year-old rock from South Africa, making them possibly the oldest life forms confirmed to date.

Researchers from the University of Tokyo and elsewhere say a close genome analysis may offer insights into animal evolution, although how long the unearthed microbes have survived remains unknown.

The rock comes from the Bushveld Igneous Complex in northeastern South Africa, according to the team’s Oct. 2 announcement.

The unique geological formation came into existence 2 billion years ago when magma rose from the underground mantle to cool and solidify. The complex is more than 7 kilometers thick and extends 500 km from east to west and 250 km from north to south.

Yohey Suzuki, an associate professor of earth and planetary science at the University of Tokyo, and his colleagues were part of the International Continental Scientific Drilling Program (ICDP).

They analyzed a sample dug out from a depth of 15 meters during a survey to examine in detail.

Utilizing a specialized chemical to detect DNA, the team realized that cells with DNA existed in huge numbers within. Proteins deriving from microorganisms’ cells were also detected, prompting the research team to conclude “living microbes are present in the rock.”

The rock specimen was cleaned and sterilized to prevent contamination by water- and air-borne microbes during drilling and transfer procedures. Only a section confirmed to be free from external water immersion was examined.

According to Suzuki’s accounts, the Bushveld Igneous Complex has experienced little degradation over the past 2 billion years. Plus, Suzuki said the rock’s composition itself protected the specimen from contamination.

“The section from which DNA was discovered is surrounded by clay, so it is unlikely that microorganisms have entered the rock from the outside,” he said.

The research findings have been published in the international academic journal Microbial Ecology at (https://doi.org/10.1007/s00248-024-02434-8).

There are already reports of living microorganisms from prehistoric times being discovered in 250-million-year-old rock salt in New Mexico, as well as strata dating back more than 100 million years on the bottom of the South Pacific Ocean.

The latest case possibly represents the oldest living microorganisms known to date, but there is no way of telling.

A caveat was provided by Ken Takai, head of the Institute for Extra-cutting-edge Science and Technology Avant-garde Research of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), who specializes in microbiology.

“Closely analyzing DNA from the microbes spotted in this rock may help trace evolutionary processes in greater detail,” Takai said. “However, it will be extremely difficult to determine the era to which the microorganisms belong, whether 2 billion years ago or more recent.”

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