This research was supported by grants from the ERC (grant no. 615253, OntoTransEvol) and German Research Council (DFG, grant nos. SFB 873 and KA 1710/4-1) to H.K., by the CellNetworks Postdoc Fellowship and EMBO Long-Term Fellowship to F.M. (grant no. ALTF 591-2017), and by the Australian Research Council (grant no. FT160100267) to F.G. and by the Novo Nordisk Foundation (grant no. NNF21OC0069913) to K.A. and (grant no. NNF18OC0031004) to M.H.S. The use of all other mammalian samples for the type of work described in this study was approved by ERC ethics screening panels (ERC starting grant no. 242597, SexGenTransEvolution and ERC consolidator grant no. 615253, OntoTransEvol).