Toxic personality? You could evolve the venom to go with that

Humans could evolve to become venomous like snakes and spiders, after a study found we have the same “genetic foundation”.

Scientists have found the genetic building blocks needed for oral venom to evolve are present in both reptiles and mammals, and said their study showed the first concrete evidence of a link between venom glands in snakes and salivary glands in mammals.

In fact, they say the two are so similar that saliva glands could be “repurposed” if the environment changed, meaning mammals such as mice – which already have some toxins in their spit – could develop venom.

The research, published in the PNAS journal, indicates that human genomes also have the potential to become venomous under certain ecological conditions.

Study author Agneesh Barua described venom as “a cocktail of proteins” used by animals to immobilise and kill prey or use for self-defence.

Previously, scientists have focused on the genes – like a set of biological instructions – that tell an organism if and how to produce the proteins that make up the toxic mixture. But Barua explained this was the wrong path to look down.

He said: “Many of the toxins currently found in venom were incorporated after the oral venom system was already established.

“We needed to look at the genes that were present before venom’s origin, genes which enabled the rise of venom systems.”

For their research, scientists from the Okinawa Institute of Science and Technology Graduate University (OIST) and the Australian National University looked for genes that work alongside and interact with the venom genes.

They used venom glands from the Taiwan habu snake – a pit viper found in Asia – and identified about 3,000 of these “co-operating” genes, noting they played important roles in protecting the cells from stress caused by producing lots of proteins.

The researchers also looked at the genomes of mammals such as dogs, chimpanzees and humans, and found they contained their own versions of such genes. The genes had a similar pattern of activity to that seen in snake venom glands, leading to the conclusion that salivary glands in mammals and venom glands in snakes share an ancient functional core.

Mr Barua said: “Many scientists have intuitively believed this is true, but this is the first real solid evidence for the theory that venom glands evolved from early salivary glands.

“While snakes then went crazy, incorporating many different toxins into their venom and increasing the number of genes involved in producing venom, mammals like shrews produce simpler venom that has a high similarity to saliva.”

The researchers said the apparent ease with which saliva glands could be switched over to producing venom was “startling”. Mr Barau called the discovery “unsettling” and joked: “It definitely gives a whole new meaning to a toxic person.”

He said experiments in the Eighties had shown that male mice “produce compounds in their saliva that are highly toxic when injected into rats”.

Mr Barua continued: “If under certain ecological conditions, mice that produce more toxic proteins in their saliva have better reproductive success, then in a few thousand years, we might encounter venomous mice.”

He added that although it was unlikely, if the right ecological conditions ever existed, humans also had the potential to become venomous.