Nearly half of the human genome consists of transposable elements, mobile genetic fragments with viral origins that can clip themselves out and re-root elsewhere in DNA. While long dismissed as genomic junk or disruptive parasites, researchers are finding that these jumping genes supply raw material for new biological adaptations. Their activity has shaped fundamental traits across species, including the evolution of mammalian placentas and gene regulation.
It is easy to slip into teleology here, treating parasitic DNA as a clever architect rather than a persistent infection that hosts eventually learned to harness. We still understand very little about how the host genome manages to co-opt such a vast and potentially destructive internal library without breaking down entirely. Worth reading for anyone interested in how genomic complexity arises from molecular friction rather than clean design.
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