Scientists have discovered the zebrafish's "social cow" gene

Researchers at Queen Mary University of London have demonstrated that zebrafish can provide genetic baz1b cues
for the evolution of social behavior in humans and domestic species.

The study, published in iScience, looked at genetically modified zebrafish
that are unable to make the baz1b protein.
The findings suggest that the gene is not only a cornerstone of physical and behavioral changes in fish and other domesticated species, but may also be the cornerstone
of human social relationships.
Domestic species, such as dogs and cats, show genetic differences, including variations
in the baz1b gene, compared to wild species.
These genetic changes are associated with physical and behavioral traits, including smaller facial features such as skulls and teeth, as well as good social behavior, closeness to humans, less aggression, and less fear
.

However, research has also shown that modern humans domesticated themselves
after separating from their extinct close relatives Neanderthals and Denisovans.
Along the way, we experience similar physical and behavioral changes
.
These changes are related to
a decrease in the number of stem cells in domesticated animals called neural crest stem cells.
The study, led by Queen Mary's team, builds on this and examines the effects of removing the function of the baz1b gene, as well as the effects
of doing so on neural crest development and social behaviour.

The study found that mutant zebrafish were more socially inclined to socialize
than zebrafish with baz1b function.
They show an increasing tendency to interact with members of the same species, although the differences between the two zebrafish are no longer pronounced by the time the fish are three weeks old
.

In addition to being more sociable, mutant zebrafish show unique facial changes
in later life.
These changes include changes in eye length and width, a prominent forehead, and a shorter nose
.
At the same time, anxiety-related behaviors were reduced
.

To measure this, the researchers examined zebrafish' responses to brief flashes of light, specifically the distance they marched within five minutes of flashing, as well as their responses to acoustic startles and exposure to new environments
.
In all cases, mutant zebrafish recovered faster after the condition changed, indicating fewer
fear-related responses.
Mutant zebrafish also exhibit mild neural crest hypoplasia
at the juvenile stage.

The study determined that in zebrafish, the baz1b gene influences morphological and behavioral traits
associated with domestication syndrome in other species.

Co-author Jose Vicente Torres Perez, from Queen Mary University of London and the University of Valencia, said: "The process of self-domestication has led modern humans to form larger social groups, among other traits, similar to the domestication process of other 'domesticated' species, and our research has the potential to help us unravel the biological roots
that govern these behaviours.
" Our study supports the existing hypothesis that behavioral and morphological changes brought about by animal and human domestication can be traced back to underdevelopment
of neural crest stem cells.
”

Caroline Brennan, lead author of the study and professor of molecular genetics at Queen Mary University of London, added: "This study provides an interesting perspective
on the origins of how we interact with others.
While generalizing the conclusions drawn from zebrafish to other vertebrates may be challenging, comparative studies like this could provide insight into the evolution
of human cognition.
”

Zebrafish were selected in part for research because about 80 percent of the genes associated with human disease have corresponding homologous genes—genes from different species that evolved from a common ancestor—making zebrafish an ideal model
for studying genetic and neuronal circuitry for potential behavior.