Evolution seminars

Brains do not fossilise, but as they grow and expand during fetal and infant development, they leave an imprint in the bony braincase. Such imprints of fossilised braincases provide direct evidence of brain evolution, but the underlying biological changes have remained elusive. Combining data from fossil skulls, ancient genomes, brain imaging and gene expression helps shed light on the evolutionary changes shaping the human brain. I will highlight two examples separated by more than 3 million years: the evolution of brain growth in Lucy and her kind, and differences between modern humans and Neanderthals.

Eyes abound in the animal kingdom. Some are large as basketballs and others are just fractions of a millimetre. Eyes also come in many different types, such as the compound eyes of insects, the mirror eyes of scallopsor our own camera-like eyes. Common to all animal eyes is that they serve the same fundamental role of collecting external information for guidingthe animal’s behaviour. But behaviours vary tremendously across the animal kingdom, and it turns outthis is the key to understand how eyes evolved. The lecture will take a tour from the first animals that could only sense the presence of light, to those that saw the first crude image of the world and finally to animals that use acute vision for interacting with otheranimals. Amazingly, all these stages of eye evolution still exist in animals living today, and this is how we can unravel the evolution of behaviours that has been the driving force behind eye evolution

Over the last fifteen years, Simona Ginsburg and I developed an evolutionary approach for studying basic consciousness, suggesting that the evolution of learning drove the evolutionary transition to from non-conscious to conscious animals. I present the rationale underlying this thesis, which has led to the identification of a capacity that we call the evolutionary transition marker, which, when we find evidence of it, we have evidence that the major evolutionary transition in which we are interested has gone to completion. I then put forward our proposal that the evolutionary marker of basic consciousness is a complex form of associative learning that we call unlimited associative learning (UAL), and that the evolution of this capacity drove the transition to consciousness. I discuss the implications of this thesis for questions pertaining to the neural dynamics that constitute conscious, to its taxonomic distribution and to the ecological context in which it first emerged. I end by pointing to some of the ways in which the relationship between UAL and consciousness can be experimentally tested in humans and in non-human animals.

Bacteria exhibit a bewildering diversity of morphologies, but despite their impact on nearly all aspects of life, they are frequently classified into a few general categories, usually just “spheres” and “rods.” Curved-rod bacteria are one simple variation observed in many environments, particularly the ocean. However, why so many species have evolved this shape is unknown. We used a regularized Stokeslet Boundary Element Method to model the motility of flagellated, curved bacteria. We show that curvature can increase swimming efficiency, revealing a widely applicable selective advantage. Furthermore, we show that the distribution of cell lengths and curvatures observed across bacteria in nature is predicted by evolutionary trade-offs between three tasks influenced by shape: efficient swimming, the ability to detect chemical gradients, and reduced cost of cell construction. We therefore reveal shape as an important component of microbial fitness.

Analogies, broadly defined, map novel concepts onto familiar concepts, making them essential for perception, reasoning, and communication. We argue that analogy-building served a critical role in the evolution of cumulative culture, by allowing humans to learn and transmit complex behavioural sequences that would otherwise be too cognitively demanding or opaque to acquire. The emergence of a protolanguage consisting of simple labels would have provided early humans with the cognitive tools to build explicit analogies and to communicate them to others. This focus on analogy-building can shed new light on the coevolution of cognition and culture, and addresses recent calls for better integration of the field of cultural evolution with cognitive science. This talk will address what cumulative cultural evolution is, how we define analogy-building, how analogy-building applies to cumulative cultural evolution, how analogy-building fits into language evolution, and the implications of analogy-building for causal understanding and cognitive evolution.

Narratives of human evolution have focused on cortical expansion and increases in brain size relative to body size, but considered that changes in life history, such as in age at sexual maturity and thus the extent of childhood and maternal dependence, or maximal longevity, are evolved features that appeared as consequences of selection for increased brain size, or increased cognitive abilities that decrease mortality rates, or due to selection for grandmotherly contribution to feeding the young. Here I build on my recent finding that slower life histories universally accompany increased numbers of cortical neurons across warm-blooded species to propose a simpler framework for human evolution: that slower development to sexual maturity and increased post-maturity longevity are features that do not require selection, but rather inevitably and immediately accompany evolutionary increases in numbers of cortical neurons, thus fostering human social interactions and cultural and technological evolution as generational overlap increases.

Natural selection affects not only selected alleles, but also indirectly affects all genes near selected sites on the genome. An increasing body of evidence suggests that this linked selection is an important driver of evolutionary dynamics throughout the genomes of many species, implying that we need to substantially revise our basic understanding of molecular evolution. This session brings together early-career researchers working towards a quantitative understanding of the prevalence and effects of linked selection.

In the last 500 million years, the dorsal telencephalon changed like no other region of the vertebrate brain. Differences range from the six-layered neocortex of mammals, to the small three-layered cortex of reptiles, and the complete absence of lamination in birds. These anatomical differences have prompted endless discussions on the origins and evolution of the cerebral cortex. We have approached this problem from a cell type and transcriptomics perspective. This reveals a more granular picture, where different cell types and classes have followed independent trajectories of evolutionary change. In this presentation, I will discuss how the molecular analysis of cell types in the brains of turtles, lizards and amphibians is updating our views on the evolution of the cerebral cortex, and the new questions emerging from these results.