Humans could evolve to a point where, at some point in the distant future, our saliva could be poisonous, similar to that of a snake, according to a new study.
Researchers at the Okinawa Institute of Science and Technology Graduate University looked for genes that alongside and interact with venom in pit viper snakes.
They found that the genetic basis required for oral venom to evolve is present in both reptiles and mammals, suggesting that humans could evolve to spit venom.
The study also provides the first concrete evidence of an underlying molecular link between snake venom glands and mammalian salivary glands.
The Taiwan habu (Protobothrops mucrosquamatus) is an invasive species that is well established in Okinawa. Researchers mapped the ‘poison genes’
VENOM: A NATURAL POISON IN ANIMALS
Poison is a form of poison that is excreted by animals from all over the animal kingdom.
It evolved in predators as well as prey as a defense mechanism.
They kill through necrotoxins, cytotoxins that kill cells, neurotoxins that affect the nervous system, and myotoxins that go to muscles.
Unlike other toxins, it is released through a bite, sting, or similar action, rather than simply being ingested.
Poisons have been good and bad for humans, killing tens of thousands of people each year, but they are also the basis for curing many diseases.
The only known poisonous mammals are solenodons, shrews, vampire bats, male platypuses and the slow loris.
This latest study of snakes, a group of animals known and feared for their powerful bite, now reveals the ancient basis of oral venom.
“Venoms are a cocktail of proteins that animals have armed to immobilize and kill prey and for self-defense,” said lead author, Agneesh Barua.
“What’s interesting about poison is that it originated in so many different animals: jellyfish, spiders, scorpions, snakes, and even some mammals.
“While these animals have evolved different ways to deliver venom, an oral system – where venom is injected through a bite – is one of the most common.”
Previously, scientists focused on the genes encoding the proteins that make up the toxic mixture, but the new study looked at how different genes interact.
“However, many of the toxins currently found in poisons were absorbed after the oral venom system was already established,” Barua said.
“We had to look at the genes that existed before the poison originated, genes that enabled the emergence of venom systems.”
So instead, the team looked for genes that interact with and interact strongly with the venom genes, by studying the venom of the Taiwanese habu snake.
The researchers identified about 3,000 of these ‘cooperating’ genes and found that they played an important role in protecting the cells from stress caused by the production of many proteins.
The genes were also key in regulating protein modification and folding.
When proteins are made, the long chains of amino acids must collapse in a specific way. Misfolded proteins can also build up and damage cells.
Like a wrong fold when making origami, one misstep prevents the protein from taking the required shape it needs to function properly.
“The role of these genes in the unfolded protein response pathway makes sense, as venom is complex mixtures of proteins,” explains Barua.
‘In order for you to be able to make all of these proteins, you need a robust system to ensure that the proteins are folded correctly so that they can function effectively.’
King Cobra (Ophiophagus hannah) The longest venomous snake in the world. While humans cannot produce poison today, they have the genetic ability to do so
PEOPLE CAN BE BORN WITH A FEAR OF SNAKES AND SPIDERS
Researchers from MPI CBS in Leipzig, Germany and Uppsala University in Sweden conducted one study who discovered that even in infants a stress reaction occurs when they see a spider or snake.
They found that this happens as early as six months old, when babies are still very immobile and haven’t had much opportunity to learn that these animals can be dangerous.
“When we showed the babies pictures of a snake or a spider instead of a flower or a fish of the same size and color, they responded with significantly larger pupils,” said Stefanie Hoehl, lead investigator of the underlying study and neuroscientist at MPI. CBS and the University of Vienna.
Under constant light conditions, this change in pupil size is an important signal for the activation of the noradrenergic system in the brain, which is responsible for stress responses.
“Accordingly, even the youngest babies seem to be stressed out by these groups of animals.”
The researchers concluded that the fear of snakes and spiders is of evolutionary origin, and as with primates or snakes, mechanisms in our brains allow us to identify objects and respond to them very quickly.
The researchers then looked at the genomes of other creatures in the animal kingdom, including mammals such as dogs, chimpanzees, and humans, and found that they contain their own versions of these genes.
When the team looked at salivary gland tissues in mammals, they found that the genes had a similar activity pattern to that seen in snake venom glands.
The scientists therefore believe that salivary glands in mammals and venom glands in snakes share an ancient functional nucleus that has been maintained since the two split lines hundreds of millions of years ago.
“Many scientists intuitively thought this to be true, but this is the first really solid evidence for the theory that venom glands evolved from early salivary glands,” Barua said.
And while snakes went mad then, taking in many different poisons into their venom, and increasing the number of genes involved in producing venom, mammals like shrews produce simpler venom that closely resembles saliva. ‘
The apparent ease with which the function of salivary glands can be repurposed to be toxic is astonishing, he explained, adding that it could mean scientists are looking at other mammals in a disturbing new light.
“There were experiments in the 1980s that showed male mice produce compounds in their saliva that are highly toxic when injected into rats,” Barua said.
“If, under certain ecological conditions, mice that produce more poisonous proteins in their saliva have better reproductive success, we may encounter poisonous mice in a few thousand years.”
Whether or not mice are on this evolutionary path is a matter that needs further investigation, but it certainly blurs the line between poisonous and non-poisonous species.
And while it’s highly unlikely, humans too could become toxic if the right ecological conditions ever existed.
“It certainly gives a whole new meaning to a toxic person,” Barua joked.
The findings are published in the journal Proceedings of the National Academy of Sciences
DNA: A COMPLEX CHEMICAL PRODUCT THAT COLLECTS GENETIC INFORMATION IN ALMOST ALL ORGANISMS
DNA, or deoxyribonucleic acid, is a complex chemical in almost all organisms that contains genetic information.
It is located in chromosomes, the cell nucleus, and almost every cell in a person’s body has the same DNA.
It is composed of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
The structure of the double helix DNA comes from adenine binding with thymine and cytosine binding with guanine.
Human DNA is made up of three billion bases, and more than 99 percent of it is the same in all humans.
The order of the bases determines what information is available to sustain an organism (similar to the way letters of the alphabet form sentences).
The DNA bases pair with each other and also attach themselves to a sugar molecule and a phosphate molecule, which together form a nucleotide.
These nucleotides are arranged in two long strands that form a spiral called a double helix.
The double helix looks like a ladder with the base pairs forming the rungs and the sugar and phosphate molecules forming vertical sidebars.
Recently, a new form of DNA was discovered for the first time in living human cells.
Named i motif, the shape looks like a twisted ‘knot’ of DNA instead of the familiar double helix.
The function of the i-motif is unclear, but experts believe it could be to ‘read’ DNA sequences and convert them into useful substances.
Source: US National Library of Medicine