Phylogenies can be used to test hypotheses about evolution. Before phylogenies became a standard tool within biology, many biologists assumed that the orb-weaving spiders, with their intricate and orderly webs, had evolved from spiders with disorderly cobweb-like webs. However, the cladistic analysis of these spiders showed that, in fact, orb-weaving was the ancestral state, and that cobweb-weaving had evolved from spiders with more orderly webs. The phylogeny caused the biologists to reject their original hypothesis about orb-weaving evolution.
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