Frietson Galis

Frietson Galis

Our research focuses on innovations and mechanisms that facilitate or constrain evolutionary changes of body plans . We want to understand questions such as: Why do we have two eyes, two lungs, four limbs and seven neck vertebrae. To understand this, we study both why such traits can hardly ever change in evolution and why, exceptionally, changes are possible. Our data have implications for biodiversity, human morbidity and lethality.


Body plan evolution, developmental constraints, phylotypic stage, vertebral column, digits, human evolution, Evo-Devo, regeneration, parthenogenesis, cichlids, phenotypic plasticity, cognitive science



  • Conservation of phylotypic stages
  • Conservation of the number of seven neck vertebrae in mammals
  • Why is the number of trunk vertebrae variable in slow mammals, but conserved in fast ones, including humans
  • Evolution of digit numbers
  • Developmental constraints against parthenogenesis

The main focus of our research is the evolution of body plans in vertebrates. The key to the understanding is the early phylotypic stage. Most organs appear during this highly conserved stage. As a consequence, the number and early development of many organs is also highly conserved, e.g. the number of eyes, ears, limbs, digits, and lungs in vertebrates, and the number of neck and trunk vertebrae in mammals. We have found strong support for the important role of developmental constraints in shaping the evolution of body plans. 


Photographs: Joris van Alphen

Skeleton hallway - Joris van Alphen
Dorcas Gazelle skeleton - Joris van Alphen


Developmental constraints-Phylotypic stages-Evolution and development of the vertebral column-Evolution and development of digits-Phenotypic plasticity-Parthenogenesis-Regeneration


All publications