Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Jun 28;284(1857):20171065.
doi: 10.1098/rspb.2017.1065.

Island Rule, Quantitative Genetics and Brain-Body Size Evolution in Homo floresiensis

Affiliations
Free PMC article

Island Rule, Quantitative Genetics and Brain-Body Size Evolution in Homo floresiensis

José Alexandre Felizola Diniz-Filho et al. Proc Biol Sci. .
Free PMC article

Abstract

Colonization of islands often activate a complex chain of adaptive events that, over a relatively short evolutionary time, may drive strong shifts in body size, a pattern known as the Island Rule. It is arguably difficult to perform a direct analysis of the natural selection forces behind such a change in body size. Here, we used quantitative evolutionary genetic models, coupled with simulations and pattern-oriented modelling, to analyse the evolution of brain and body size in Homo floresiensis, a diminutive hominin species that appeared around 700 kya and survived up to relatively recent times (60-90 kya) on Flores Island, Indonesia. The hypothesis of neutral evolution was rejected in 97% of the simulations, and estimated selection gradients are within the range found in living natural populations. We showed that insularity may have triggered slightly different evolutionary trajectories for body and brain size, which means explaining the exceedingly small cranial volume of H. floresiensis requires additional selective forces acting on brain size alone. Our analyses also support previous conclusions that H. floresiensis may be most likely derived from an early Indonesian H. erectus, which is coherent with currently accepted biogeographical scenario for Homo expansion out of Africa.

Keywords: Homo floresiensis; Island Rule; adaptive evolution; brain–body size correlation; dwarfing; evolutionary genetics.

Conflict of interest statement

We declare we have no competing interests.

Figures

Figure 1.
Figure 1.
Mapping the frequency of rejecting the neutrality hypothesis for the differentiation of body size between H. erectus and H. floresiensis according to Turelli's MDE model, along time for divergence and effective population size.
Figure 2.
Figure 2.
Relationship of selection gradient β (approximating mean-standardized selection gradient βµ) for the differentiation of body size between H. erectus and H. floresiensis with time for divergence in the simulations.
Figure 3.
Figure 3.
Distribution of expected brain size (EBS, in cubic centimetres) of Homo floresiensis under correlated evolution with body size evolution from H. erectus with ancestral brain sizes ranging from 750 cm3 to 1000 cm3 (a). Distribution of expected ancestral brain sizes (EABS) leading to the evolution of brain and body size values of H. floresiensis (b).

Similar articles

See all similar articles

Cited by 2 articles

LinkOut - more resources

Feedback