Évolution du développement et des génomes - Denis Duboule

Denis Duboule
Collège de France
Évolution du développement et des génomes
Année 2025-2026

02 - L'ADN, acteur et témoin de l'évolution des animaux : La disparition de la queue chez les grands singes

Résumé

Rappel des points importants de la leçon précédente. Histoire du locus T et clonage du gène Tbxt. Importance potentielle de ce gène dans la perte de la queue chez les hominidés, suite à un phénomène de saut d'exon spécifique aux humains et aux grands singes.

Denis Duboule
Collège de France
Évolution du développement et des génomes
Année 2025-2026

01 - L'ADN, acteur et témoin de l'évolution des animaux : L'ADN, cause proximale ou cause ultime de notre évolution ?

Résumé

Cette première leçon commencera par un rappel des principes fondamentaux de la discipline de l'évo-dévo, avec un aspect historique touchant à l'importance de l'ADN en tant que source potentielle de variations évolutives. Ensuite, le « locus T », et son importance dans le développement de la génétique moléculaire des mammifères, sera présenté, également de façon historique, avant d'arriver au clonage du gène central de ce locus, le gène Tbxt (ou T ou Brachyurie).

Denis Duboule
Chaire Évolution du développement et des génomes
Collège de France
Année 2025-2026

Nos ancêtres les poissons
Conférence - Neil Shubin : How Do New Biological Inventions Arise in Evolution? Lessons from Fossils, Embryos, and Genes

Neil Shubin
Université de Chicago, Président élu de l'Académie nationale des sciences (NAS), États-Unis

Résumé

When we look at the history of life at a grand scale, from the earliest single celled organism to complex animals alive today, we see a past filled with great revolutions. Major transformations pervade this history, involving new features, new developmental processes, new ways of living, and new ecological interactions. In our own lineage, over the past 500 million years some fish evolved to live on land, reptiles evolved to fly, and primates evolved the ability to talk, walk, and think. For each of these major transitions we recognize features that allowed them to happen. The standard view is that these innovations were enablers for a major revolution: for example, feathers arose for flight, lungs, for life on land, etc. But this view couldn't be farther from the truth. Lungs evolved in fish well before they ever took steps on land, feathers arose in dinosaurs before they could fly, and so on. The features that play a role in great evolutionary changes arise by repurposing existing features for new functions. This view of evolutionary tinkering, first pioneered by François Jacob in the 1970's, carries profound implications for modern molecular and paleontological evolutionary biology.

Denis Duboule
Chaire Évolution du développement et des génomes
Collège de France
Année 2025-2026

Nos ancêtres les poissons
Conférence - Neil Shubin : The Evolutionary Origins of Bones and Teeth

Neil Shubin
Université de Chicago, Président élu de l'Académie nationale des sciences (NAS), États-Unis

Résumé

Teeth and bones are fundamental features of vertebrate organisms. The earliest vertebrates date from fossils that are over 500 million years old and existed at the time of the Cambrian Explosion, a great burst of innovation in the evolutionary history. The first creatures with tissues similar to our teeth and bones aren't seen until tens of millions of years later. Some of these reports have been controversial because challenges imaging the fossils and comparing the tissues between fossil and living forms. New imaging technologies have transformed our ability to study this issue. Studies from multiple laboratories have revealed that tissues equivalent to our teeth and bones originally evolved outside the body—in the bony exoskeletons of our jawless fish ancestors. Inside this exoskeletal armor are small structures that are distinctly toothlike. Detailed comparisons of these features among living and fossil vertebrates and invertebrates reveal that the earliest teeth likely had a sensory function in the external tissues of these fish. Assessing diverse fossil fish reveals that many distinct features of our bones and teeth, such as the capacity to remodel, originally came about in jawless fish.

Denis Duboule
Chaire Évolution du développement et des génomes
Collège de France
Année 2025-2026

Nos ancêtres les poissons
Conférence - Neil Shubin : Discovering How Fish Evolved to Walk

Neil Shubin
Université de Chicago, Président élu de l'Académie nationale des sciences (NAS), États-Unis

Résumé

The ability to walk is fundamental to human lives. Like all our biological features walking has a complex and deep history. It is most commonly thought that walking arose as fish made the evolutionary transition to land, shifting from an aquatic environment to a terrestrial one. In this view, the transition out of water meant that animals now had to evolve new mechanisms to deal with gravitational loads. As a consequence, they developed more mobile joints, arm and leg bones with robust connections for expanded locomotory muscles, and other structures to allow them to move about. Surprising, this very intuitive view is not supported either by comparative anatomy or the fossil record. The closest fish relatives to terrestrial vertebrates were capable of walking with four appendages, a fact seen in the structure of the bones and joints in their fins. Moreover, walking either on four appendages or two is commonly seen in aquatic fish ranging from sharks, lobe fin fishes, and diverse ray finned fishes. Indeed, many of these fish use alternating gaits and appendage motions in aquatic settings that are similar to terrestrial tetrapods. This observation leaves open the question of why fish walk in water instead of swimming. To answer these questions scientists have developed underwater treadmills, experiments training fish to walk, and robots that simulate walking behaviors. One major factor in the origin of fish walking, hence our own, is energetics: at slow speeds, and in certain environmental conditions is it energetically more efficient to walk than swim.