Morphological variation in brain through domestication of fowl

Abstract

Great variations in the size, shape, color, feather structure and behavior are observed among fowl breeds. Because many types of domestic fowls have been bred for various purposes, they are ideal to assess the relationship between brain morphology and avian biology. However, little is known about changes in brain shape that may have occurred during fowl domestication. We analyzed the brains of red jungle fowl and domestic fowl to clarify differences in the brain shape between these breeds, as well as the shape changes associated with size enlargement using three-dimensional geometric morphometrics. Principal component and multivariate regression analyses showed that ventrodorsal bending, anteroposterior elongation and width reduction were significantly correlated with brain size. According to the size-dependent analysis, the red jungle fowl brain has an intermediate shape between the brain of young broilers and that of large domestic fowl and adult broilers. After the size effect is removed, geometric morphometric analyses show that the brain of red jungle fowl is different from that of domestic fowl, with large round cerebral hemispheres. Significant correlations exist between the skull length and brain volume among fowl, while the brain volume relative to the skull length is distinctly larger in red jungle fowl compared with domestic fowl. The distinct brain shape and increased relative brain size of red jungle fowl may be driven by the presence of large, rounded cerebral hemispheres.

Morphological variation under domestication: how variable are chickens?

“…We have summarized additional skeletal cranial differences, which add to the here confirmed major differences between fowl and chickens and within chickens as revealed by PCA, in table 7. The difference in brain case shape between fowl and chickens and the variation in domesticated chicken breeds can be explained by the huge variation in brain shape and its reformation processes during ontogeny [60][61][62]. Regarding the variation in the upper premaxillary and nasal processes, we have no knowledge on the prevalence of the 'gap' in the upper beak in other crested breeds.…”

An Evolutionary Perspective on Why Food Overconsumption Impairs Cognition

“…An understanding how food scarcity-based adaptations drove human brain evolution provides insight into how removal of this environmental challenge affects cognition and cellular neuroplasticity. One clue comes from data showing that the overall brain size of domesticated animals is reduced compared to the wild species from which they originated, including farm animals raised for meat production (chickens, pigs and cattle) and pets (dogs and cats) [26][27][28]. A common environmental factor that might account for the reduction in brain size is that domesticated animals no longer have to devote cognitive and physical exertion to acquire food.…”

Association of tameness and sociability but no sign of domestication syndrome in mice selectively bred for active tameness

“…The selected foxes not only exhibited changes in behaviour, 5,8 but also displayed changes in phenotypical features, such as reduced snout length, smaller teeth, floppy ears, decreased brain size, depigmentation, and frequent oestrus cycles 5,8,9 . Similar changes in the brain and cranial morphology have also been observed in cattle, 10 camelids, 11 rabbits, 12 chickens, 13 fowl, 14 cats, 15 rats, 16 and various other mammals 17 . Some morphological changes associated with domestication have also been reported in the skulls of wild foxes living in cities 18 .…”