Interesting, because 300 million years ago, harvestmen (like spiders) were much the same as today. Said one researcher, “It is absolutely remarkable how little harvestmen have changed in appearance since before the dinosaurs.”
Yet changes do happen. From ScienceDaily:
Called after Tolkien’s character from the “Lord of the Rings” series, a new eyeless harvestman species was found to crawl in a humid cave in southeastern Brazil. Never getting out of its subterranean home, the new daddy longlegs species is the most highly modified representative among its close relatives and only the second one with no eyes living in Brazil.
While there are cave dwellers that can easily survive above the ground and even regularly go out in order to feed or mate, there are some, such as the new harvestman species, Iandumoema smeagol, that never leave their subterranean habitats. As an adaptation, the new harvestman species is eyeless and has a reduced amount of melanistic pigmentation, which shows through its pale yellowish colours. More.
Could the eyes be bred back in? It’s worth considering, if we consider the history of the blind cave fish:
Losses can be reversed. Blind Mexican cavefish are considered an excellent model for studying evolution, with revealing results. In the lab, researchers have mated blind cave fish from separate and distant underwater caves and produced sighted offspring. Apparently, separate mutations had produced the blindness, and some hybrid offspring inherited a mix that includes enough genes for functioning sight. So no irrevocable devolution had taken place after all.
We shall see.
See also: Devolution: Getting back to the simple life
Stasis: Life goes on but evolution does not happen
– A new species of troglobitic harvestman, Iandumoema smeagol sp. n., is described from Toca do Geraldo, Monjolos municipality, Minas Gerais state, Brazil. Iandumoema smeagol sp. n. is distinguished from the other two species of the genus by four exclusive characteristics – dorsal scutum areas with conspicuous tubercles, enlarged retrolateral spiniform tubercle on the distal third of femur IV, eyes absent and the penial ventral process slender and of approximately the same length of the stylus. The species is the most highly modified in the genus and its distribution is restricted only to caves in that particular area of Minas Gerais state. The type locality is not inside a legally protected area, and there are anthropogenic impacts in its surroundings. Therefore, Iandumoema smeagol sp. n. is vulnerable and it must be considered in future conservation projects. Open access – Ricardo Pinto-da-Rocha, Rafael Fonseca-Ferreira, Maria Bichuette. A new highly specialized cave harvestman from Brazil and the first blind species of the genus: Iandumoema smeagol sp. n. (Arachnida, Opiliones, Gonyleptidae). ZooKeys, 2015; 537: 79 DOI: 10.3897/zookeys.537.6073