“Island dwarfism” and the “Hobbits”

The tiny size of the “hobbits” (Homo floresiensis) found on Flores in the Indonesian Archipelago presents a puzzle. One proposed solution is that these people were affected by “island dwarfism”.

However, as I wrote as a comment on this article:

I have two problems with this thesis. One is that Flores is not some tiny speck of land. Check it on an atlas. It is quite a large island. Also, there is no other evidence of island dwarfism in humans (people on Pacific islands tend to be larger than average if anything).

Secondly, there are several perfectly good examples of dwarfed human populations that are associated with one feature of the environment, namely life under the rainforest canopy. I understand that the palaeoenvironment on Flores has been proposed to be rainforest.

This island dwarfism idea keeps popping up to explain the tiny stature of Homo floresiensis. I don’t understand its appeal myself.

As it happens, I have proposed a theory for the short stature of Pygmies and Negritos based on their rainforest environment, and I suggested in a comment from the floor at a human biology conference several years ago that this factor might have been at play in producing the tiny skeletal size of Homo floresiensis. Some details are at this Wikipedia article.

Advertisements

8 responses to this post.

  1. I like your theory for the short stature of Pygmies and Negritos based on their rainforest environment. Not too sure about it being an adaptation to low ultraviolet light levels because it seems like that lighter skin would have be selected for over time like with the Eskimo–Aleut.

    Reply

    • Posted by Julian O'Dea on September 28, 2016 at 11:45 am

      Pygmies and some “Negritos” do have lighter skin than the groups around them. The reduced skeleton and hence body size might have been an additional adaptation. The level of ultraviolet light in rainforest is about 1% of that outside (according to measurements I once took in a North Queensland rainforest near Cairns.)

      Reply

  2. People on Pacific Islands haven’t been there long enough to evolve island dwarfism, have they?

    Regarding your point about the size of Flores: Dwarf elephant fossils have been found on Cyprus, Malta, and Sicily, all on the same order of size as Flores. And Flores, Sulawesi, and Timor as well.

    However, jungle dwarfism is obviously well documented in humans, and I agree it would seem very strange if Flores were an exception.

    No reason it couldn’t be both, of course.

    Reply

    • Posted by Julian O'Dea on September 28, 2016 at 2:25 pm

      Yes. That is probably a fair point about the Pacific islands although the trend seen has been towards larger body size.

      Claims that Flores is a place of island dwarfism ignore the endemic giant rat:

      https://en.m.wikipedia.org/wiki/Flores_giant_rat

      as well as the Komodo dragons there.

      Reply

      • IIRC small animals get larger and large animals get smaller in insular environments. But I already mentioned not being a biologist.

        I hadn’t known there was a documented trend of Pacific Islanders getting larger over time. I misunderstood you. That’s a very interesting point if so.

  3. Posted by Julian O'Dea on September 29, 2016 at 1:53 pm

    http://blog.everythingdinosaur.co.uk/blog/_archives/2015/03/15/those-highly-adaptable-humans.html

    “It is very likely that H. erectus also adapted to forested regions. In addition, the mysterious Homo floresiensis, fossils of which come from the remote Indonesian island of Flores was very well adapted to its mostly forested island home. H. floresiensis may have survived to 13,000 years ago, but islanders talk of stories of strange little people living in the forest from much more recent times, perhaps until just a few hundred years ago.”

    Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: