Is the Homo floresiensis phenotype due to mutations in the PCNT gene?

Again with more confusing back and forthing…. but this time we leave the Neandertals and focus in on debate over whether or not Homo floresiensis is a novel species. New research published in Science, focuses in on the discovery of a mutation in a gene that causes a rare growth condition called MOPD II. People who are diagnosed with MOPD II have small brains and body size but near-normal intelligence which is what we see evident in the skeletal remains of Homo floresiensis and the associated archaeological artifacts. The MOPD stands for microcephalic (or Majewski) osteodysplastic primordial dwarfism, and the Roman numeral two just stands for the type.Primordial Dwarfism

Anita Rauch is first author of this new paper, “Mutations in the Pericentrin (PCNT) Gene Cause Primordial Dwarfism.” As you can tell from the title, PCNT is the culprit here. I did a bit of sleuthing to figure out what PCNT does. I figured out it encodes a conserved centrosome protein. Centrosomes play an essential role in microtubule organization and pull chromosomes apart during cell division. Additionally, PCNT forms a large complex with gamma tubulin and other proteins involved in microtubule nucleation. Ultimately, any mutation in this gene would affect the function of this protein in cellular division and development of the organism.

The research was inspired by two unrelated tiny girls living in northern Bavaria as well as Paddy Ryan, a man living with MOPD II. If Rauch and crew’s conclusion holds up, there’s about 100 known people living today with phenotypes seen Flores like hobbits. These are people who have grown up and live with the mutations in PCNT and display the MOPD type II condition which that leads to them being normally proportioned but half-sized. I once saw a documentary on people with MOPD and had thoughts they were similar to what we call, Homo floresiensis.

Another really important part of this study is that it totally challenges the primitive wrist hypothesis paper that came out last September. I critiqued that paper, where the authors argued that carpal bones of the hobbit hominid display ape-like traits. I had beef in that they said the fusion of centrale in the Homo floresiensis wrist was a primitive trait, even though modern humans sometimes display this feature. Rauch addressed this as well as the other primitive traits seen in the hobbit wrists. She writes that mutations in PCNT make for bony anomalies of the hand and wrist. I’d love to read what the primitive wrist folk have to say about this.

7 thoughts on “Is the Homo floresiensis phenotype due to mutations in the PCNT gene?

  1. From what i have read the anomalies present not only in the rest of the skeleton but the internal cranial architecture shows clearly they weren’t just little people. Little people exist now and they are still normal humans except for their size. How do you conclude that so many skeletons found on that island have the same characteristics? Wouldn’t a genetic anomaly actually preclude the endurance of a primitive human species?

  2. Homo floriensis shows a number of “primitive”
    features of the postcranial skeleton that are also
    found in Australopithecus and Homo habilis.
    The “microcephalic dwarf theory” doesn’t fly.

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