What makes some animals more sociable than others? A 2018 study titled "Red Fox Genome Assembly Identifies Genomic Regions Associated with Tame and Aggressive Behaviours" provides intriguing insights into the genetic basis of social behaviour. Researchers investigating the behaviour of domesticated foxes, as part of the long-running Russian Fox Domestication Experiment, uncovered genetic links that may help explain not only the social traits of animals but also human behaviours and conditions, such as autism.
By selectively breeding domesticated foxes for tameness or aggression over decades, this groundbreaking study sheds light on the biology of behaviour and its genetic underpinnings.
Genetic and Neurological Insights
Researchers identified 103 genetic regions that differed between tame, aggressive, and control foxes, highlighting the impact of selective breeding on behaviour. Notably, 45 of these regions overlapped with genetic changes observed in domesticated dogs, hinting at a shared evolutionary basis for social behaviour across species.
Kukekova and her colleagues identified 13 genes linked to autism spectrum disorder (ASD) and 13 genes linked to bipolar disorder in humans, also present in the domesticated foxes. These findings suggest potential genetic connections between domestication and these human conditions. However, these findings are part of the early stages of research, and further studies will be necessary to fully understand the relevance of these genetic links to human behaviours, if any.
The genetic findings were complemented by neuroimaging and histological studies of brain structure. Tame and aggressive foxes exhibited distinct differences in their prefrontal cortex, a brain region involved in decision-making and social behaviours. Surprisingly, both tame and aggressive foxes had larger prefrontal cortex regions than wild foxes, despite their opposite behavioural traits.
This surprising result highlights that domestication itself, regardless of whether it was directed toward tameness or aggression, led to an increase in the size of the prefrontal cortex. This challenges the conventional view that domestication typically reduces brain size and suggests that the selection for extreme behavioral traits—whether social cooperation or aggression—may drive the expansion of neural regions involved in complex social and cognitive processing
Key Gene: SorCS1
One gene in particular, SorCS1, has drawn attention for its potential role in shaping social traits. Tame foxes—those bred to approach humans with curiosity and reduced fear—were found to carry a specific variant of SorCS1 not present in the aggressive foxes.
"The SorCS1 gene highlighted in our study has not been known to be involved in social behavior, so we think that the fox can help to identify novel behavior genes," - Anna Kukekova
SorCS1 is a gene that plays a crucial role in overall brain function, particularly in the maintenance of synapses—the connections between nerve cells. These synaptic connections are essential for the brain's ability to process information, form memories, and regulate various behaviours. The proper functioning of these connections is fundamental for a wide range of cognitive processes, including learning and decision-making.
One of SorCS1's key roles is its influence on neural plasticity, which allows the brain to adapt and change in response to experiences. This plasticity is especially important for social interaction and communication. Interestingly, variants of this gene in humans have been linked to autism spectrum disorder (ASD), a condition that affects how individuals communicate and interact with others. The connection between SorCS1 and social behaviour in both foxes and humans suggests that this gene may be involved in the broader genetic pathways that shape sociability, offering valuable insights into the genetic basis of social traits across species.
Implications of the Study
The discovery of SorCS1 variants in tame foxes highlights the role of this gene in social behaviours across species. In humans, disruptions in SorCS1 have been implicated in autism, reinforcing the idea that common genetic pathways influence social traits in both animals and humans. This connection provides valuable clues for understanding the genetic basis of conditions like ASD.
However, while the connection between the SorCS1 gene and social behaviour provides interesting insights, it is important to remember that the genetic and neurological basis of social behaviour is a polygenic trait, meaning multiple genes are likely involved in shaping social behavior, with many other factors likely contributing to the overall behavioural traits observed in both foxes and humans.
Research Methods
The researchers employed a range of scientific techniques to investigate the genetic and brain-based links to sociability, using a combination of behavioural tests, genetic sequencing, and brain imaging:
Foxes were observed in controlled settings to measure their responses to human interaction, and their genomes were analyzed to identify specific gene variants.
Advanced techniques, including RNA sequencing and quantitative PCR, were used to analyze gene expression levels, confirming significant differences in SorCS1 activity between tame and aggressive foxes.
Brain imaging studies further highlighted structural and functional changes in brain regions linked to social behaviour, offering a comprehensive view of the relationship between genes, brain structure, and behaviour.
A Model for Human Social Traits
The domesticated foxes in the Russian experiment provide a compelling model for studying the biology of social behaviour. By uncovering genetic markers like SorCS1, researchers are gaining valuable insights not only into the domestication process but also into the shared genetic roots of social behavior across species. This groundbreaking research sheds light on the evolution of social traits and underscores the complex connections between humans and animals.
The discovery of genes like SorCS1 is particularly significant for understanding human conditions such as autism spectrum disorder (ASD). However, it is crucial to acknowledge that directly translating findings from foxes to humans is not straightforward. While the study offers promising genetic insights that could inform our understanding of ASD, it does not claim that the fox model will immediately lead to breakthroughs in human research. Instead, it opens the door to further exploration into the genetic and neurological foundations of social behaviour, which may eventually have broader implications for conditions like ASD.
The Broader Context
This study is part of a larger body of work exploring the genetic and neurological underpinnings of social behaviour. Similar research has been conducted in:
Dogs: Domesticated dogs also share genetic variants with humans that influence social behaviour. Scientists found 45 breeding-influenced regions in the fox genome that also had undergone evolutionary changes in dogs. One of these regions is associated with Williams-Beuren syndrome in humans, a genetic disorder characterized by extremely outgoing, friendly behaviour.
Humans: The study raises intriguing questions about the evolutionary forces shaping social traits in humans and other species. Contrary to previous studies, both tame and aggressive strains had larger brains than the conventional, “wild” foxes. The tame and aggressive foxes also displayed similar changes to regions in the prefrontal cortex, despite being bred for opposite behaviours.
These results challenge traditional assumptions about how brain circuits relate to behaviour and evolution, as well as how domestication shapes the brain.
Summary
The research on domesticated foxes offers groundbreaking insights into the genetic and neurological underpinnings of social behaviour and the identification of the SorCS1 gene variant, crucial for social behaviour, underscores the shared genetic pathways between animals and humans, with potential implications for understanding conditions like autism spectrum disorder.
This study not only enhances our understanding of the evolution of social traits but also highlights the value of animal models in exploring human social traits. As scientists continue to uncover the intricate connections between genes, brain structure, and behaviour, these findings pave the way for future advancements in both animal and human research.
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