The Evolution of a Head Has Been Traced Back Surprisingly Far Back Our Ancestral Line - ScienceAlert
Their central nervous system is instead made up of clumps of neurons in the anterior and posterior parts of their body, with a dorsal strand connecting them both. As adults, these animals look like stagnant sponge-like blobs, with no clear head or tail.PIC Tunicate tadpole showing bipolar tail neurons (green).Their research has found Hmx genes, which encode for a pair of neurons in a tunicate tadpole's tail, are related to the genes that encode for clumps of neurons in a lamprey's head.When splicing the Hmx genes of a lamprey into a tunicate species called Ciona intestinalis, researchers found the gene helped drive the expression of bipolar tail neurons.In lampreys, however, the same genes helped drive the expression of sensory neurons in the cranium.