Short-statured Flores residents not descended from 'hobbits'

3 August 2018

A short-statured population of Indonesians living on the island of Flores arose independently of the extinct species Homo floresiensis – the so-called ‘hobbits’ – an international team of scientists has found.

The researchers, who included Professor Peter Visscher from UQ’s Institute for Molecular Bioscience and Queensland Brain Institute, showed that a group of small-bodied humans who live on the island today do not possess any genes associated with Homo floresiensis, whose remains were discovered nearby.

The findings shed new light on the evolutionary history of modern humans in Southeast Asia.

In 2003, archaeological remains of H. floresiensis were discovered on Flores, and were dated to between 60,000 and around 100,000 years old. The finding drew significant international attention in part because the skeleton was that of an adult who would have only been around one metre tall. Consequently, this group of ancient hominins were nicknamed “Hobbits”. 

The new study focusses on several families who live in the village of Rampasasa, which is located near the cave site where H. floresiensis was discovered. Many of the individuals in the village are very short-statured, with an average height just under 150 cm.

To explore the possibility that these short-statured individuals might share some ancestry with H. floresiensis, Professor Visscher and colleagues at Princeton University, the University of California Santa Cruz, and several other genetics institutes around the world examined the genomes of a number of the villagers, looking for DNA variations that might explain their small stature, and perhaps reveal H. floresiensis ancestry.

“We didn’t find any evidence of DNA from an unknown extinct hominin,” Professor Visscher said.  

Instead, the researchers found that the villagers’ genetic ancestry mostly aligns with that of people from East Asia, New Guinea and Oceania. There was also evidence of some DNA from two groups of archaic humans — Neanderthals and Denisovans — which is common in populations in this region.

Diet played a role in evolution of height

“The most interesting result was evidence for adaption, both diet-related and for reduced stature,” Professor Visscher said.

This included the discovery that people from Rampasasa possess DNA variations in genes associated with fatty acid synthesis, which is consistent with an ancestral shift toward a diet rich in omega-3 fatty acids, found in foods such as oily fish, seeds and nuts.

To understand why these people are so small, Professor Visscher and his colleagues first looked for genetic variations that contribute to reduced height in Europeans. Via the UK Biobank, they analysed the genomic data of more than 450,000 people of European ancestry and identified which variations were associated with short stature.

According to Professor Visscher, many of these variations linked with short stature show up in the genomes of the people from Rampasasa. 

"Our study shows how a powerful contemporary resource like the UK Biobank can be leveraged to address questions of human adaptation in the past,” he said.

He added that it’s likely the isolation and limited resources of the island encouraged selection of these short-stature variations over a long time period. 

"Just as livestock breeding happens through small changes in gene frequencies at very many loci, human adaption works by exploiting the pool of polygenic variation available for selection."

Professor Visscher said he was pleased with the outcome and that the study shows how genome-wide association studies (GWAS) can be leveraged to address fundamental questions about human adaptation. 

The study was published in Science, one of the world’s leading scientific journals, and funded by organisations including the Australian Research Council and National Health and Medical Research Council.