Exploring the evolution of Human-Dog Relationships

Exploring the Evolution of the Human-Dog Relationship

Lead microbiologist Bushra Schuitemaker recently attended an enlightening seminar by Dr. Anders Bergstrom of the University of East Anglia. Dr. Bergstrom, an expert in ancient DNA, presented a talk on the evolution of the human-dog relationship, shedding light on the deep-rooted connection between humans and dogs.

Dogs have been evolutionary partners with humans through agricultural evolution, serving various roles such as workers, guards, and companions. The domestication of dogs began approximately 15,000 years ago across different populations worldwide, marking a significant milestone in human history.

Genomic Insights into Dog Domestication

A pivotal study published in Nature (2022) on grey wolf genomic history reveals the dual ancestry of dogs. Grey wolves, unlike many other mammals such as cave hyenas, survived the ice age, possibly due to their ability to travel long distances. This mobility prevented population fragmentation, allowing for continued genetic diversity through interbreeding.

Convergent Evolution of Humans and Dogs

Evidence of convergent evolution between humans and dogs is compelling. Convergent evolution refers to the independent evolution of similar traits in different species. For example, humans and dogs have shown an increase in the AMY2B gene copy number, which is crucial for starch digestion. Non-agricultural populations, such as those in Australia and the Arctic, have lower AMY2B gene copy numbers, as observed in dingos. This genetic adaptation reflects the transition of humans from hunter-gatherers to agriculturalists. Although similar to modern dogs, Dingos exhibit AMY2B gene levels comparable to wolves, highlighting their unique evolutionary path.

The IFT88 gene appeared around 40,000 years ago and was once dominant in the wolf genome but is now absent in modern wolves. This gene's historical prevalence indicates beneficial mutations can rapidly spread through populations. In mice, IFT88 knockouts result in significant cranial morphological changes, such as skull and jaw structure alterations.

Genetic Markers and Evolutionary Mysteries

Research has identified significant genetic markers, such as an allele on chromosome 14 related to olfactory processes and a locus on chromosome 10 associated with drop ears and body mass. These markers transitioned from heterozygous to homozygous, suggesting a selective sweep before the diversification of wolves and dogs. The common ancestor of wolves and dogs remains unidentified, posing an intriguing mystery that may be resolved with further sampling.

The Role of the Microbiome in Evolution

There is a hypothesis that the microbiome adapted before the genome in wolves. One theory suggests that wolves may have adopted a humanised microbiome from consuming human faeces, although coprophagy is not typical behaviour for wolves.

Modern Dog Ancestry and Domestication Processes

Modern dogs share the closest genetic relationship with ancient dogs from Siberia, though these ancient dogs are not direct ancestors. Different dog populations worldwide exhibit varying degrees of relatedness to ancient dogs. For instance, Near Eastern and African dogs are genetically closest to ancient European dogs, indicating multiple populations contributed to dog domestication and genetic diversity. Western dogs contributed to the Near East's genetic pool, while Eastern dog genomes are exclusively found in Dingos and New Guinea Singing Dogs.

This research proposes two theories of domestication: one suggests a merging of Western and Eastern ancient dog populations, while the other posits that all ancient dogs originated from Eastern populations, with Western dogs integrating later. This could explain the predominance of Eastern dog genomes in certain Asian regions.

Revisiting Historical Samples

Re-testing of historical samples has revealed fascinating findings. Some specimens previously classified as dogs were identified as wolves, and vice versa, demonstrating the power of genetics to clarify ambiguities in morphological data. Notably, 4,000-year-old wolf and dog bones were discovered on a small island off Gotland, where wolves are not indigenous. This suggests humans intentionally brought them to the island, possibly reflecting our longstanding affection for dogs.

Implications for Future Research

This research enhances our understanding of dog domestication and offers potential applications for studying the domestication of other species, such as foxes. The intricate relationship between humans and dogs continues to be a rich field of study, promising further fascinating discoveries.