loading . . . Years ago, humanity lost one of its last surviving hominin cousins, _Homo floresiensis_ (also known as "the hobbit" thanks to its small stature). The cause of its disappearance, after more than a million years living on the isolated volcanic island of Flores, Indonesia, has been a longstanding mystery.
Now, new evidence suggests a period of extreme drought starting about 61,000 years ago may have contributed to the hobbits' disappearance.
Our new study, published today in _Communications Earth & Environment_, reveals a story of ecological boom and bust. We've compiled the most detailed climate record to date for the site where these ancient hominins once lived.
**Related:Scientists Finally Reveal Why 'Hobbits' Were So Small**
It turns out that _H. floresiensis_ and one of its primary prey, a pygmy elephant, were both forced away from home by a drought lasting thousands of years – and may have come face-to-face with the much larger _Homo sapiens_.
## An island with deep caves
The discovery of _H. floresiensis_ in 2003 changed our thinking on what makes us human. These diminutive, small-brained hominins, standing only 1.1 metres tall, made stone tools. Against the odds, they reached Flores seemingly without boat technology.
Bones and stone tools from _H. floresiensis_ were found in Liang Bua cave, hidden away in a small valley in the uplands of the island. These remains date to between 190,000 and 50,000 years ago.
View of the Wae Racang river looking upstream from Liang Bua towards Liang Luar. (Garry K. Smith)
Today, Flores has a monsoonal climate with heavy rainfall during wet summers (mostly from November to March) and lighter rain during drier winters (May to September).
However, during the last glacial period there would have been significant variation in both the amount of rainfall and when it arrived.
To find out what the rains were like, our team turned to a cave 700 metres upstream of Liang Bua named Liang Luar. By pure chance, deep inside the cave was a stalagmite that grew right through the _H. floresiensis_ disappearance interval.
As stalagmites grow layer by layer from dripping water, their changing chemical composition also records the history of a changing climate.
Our caving team in the deep, brooding interior of Liang Luar in 2006. (Garry K. Smith)
Palaeoclimatologists have two main geochemical tools when it comes to reconstructing past rainfall from stalagmites. By looking at a specific measure of oxygen known as d18O, we can see changes in monsoon strength. Meanwhile, the ratio of magnesium to calcium shows us the total rainfall amount.
We paired these measurements for the same samples, precisely anchored them in time, and reconstructed summer, winter, and annual rainfall amounts. All this provided unprecedented insight into seasonal climate variability.
We found three key climate phases. It was wetter than today year-round between 91,000 and 76,000 years ago. Between 76,000 and 61,000 years ago, the monsoon was highly seasonal, with wetter summers and drier winters.
Then, between 61,000 and 47,000 years ago, the climate turned much drier in summer, similar to that seen in Southern Queensland today.
## The hobbits followed their prey
So we had a well-dated record of major climate change, but what was the ecological response, if any? We needed to build a precise timeline for the fossil evidence of _H. floresiensis_ at Liang Bua.
The solution came unexpectedly from our analysis of d18O in the fossil tooth enamel of _Stegodon florensis insularis_ , a distant extinct pygmy relative of modern elephants.
The jawbone and ridged molar of an adult Stegodon florensis florensis, the large-bodied ancestor of Stegodon florensis insularis. Scale bar is 10 cm. (Gerrit van den Berg)
Juvenile pygmy elephants were one of the hobbits' key prey, as revealed by cut marks on bones in Liang Bua.
Remarkably, the d18O pattern in the Liang Luar stalagmite and in teeth from increasingly deep sedimentary deposits at Liang Bua aligned perfectly. This allowed us to precisely date the _Stegodon_ fossils and the accompanying remains of _H. floresiensis_.
The refined timeline showed that about 90% of pygmy elephant remains date to 76,000–61,000 years ago, during the strongly seasonal "Goldilocks" climate. This may have been the ideal environment for the pygmy elephants to graze and for _H. floresiensis_ to hunt them. But both species almost disappeared as the climate got drier.
Cross-section of the precisely dated stalagmite used in this study, showing growth layers. The graph shows the improved timeline for Stegodon fossils in two excavation sectors at Liang Bua. (Mike Gagan)
The decline in rainfall, pygmy elephants, and hobbits all at the same time indicates that dwindling resources played a crucial role in what appears to be a progressive abandonment of Liang Bua.
As the climate dried, the primary dry-season water source, the small Wae Racang river, may have dwindled too low, leaving the _Stegodon_ without fresh water. The animals may have migrated out of the area, with _H. floresiensis_ following.
## Did a volcano contribute too?
The last few _Stegodon_ fossil remains and stone tools in Liang Bua are covered in a prominent layer of volcanic ash, dated to around 50,000 years ago. We don't yet know if a nearby volcanic eruption was a "final straw" in the decline of Liang Bua hobbits.
The first archaeological evidence attributed to _Homo sapiens_ is above the ash. So while there is no way of knowing if _H. sapiens_ and _H. floresiensis_ crossed paths, new archaeological and DNA evidence both indicate that _H. sapiens_ were island-hopping across Indonesia to the supercontinent of Sahul by at least 60,000 years ago.
**Related:Ancient Tools Suggest Indonesian 'Hobbits' Had a Mysterious Neighbor**
If _H. floresiensis_ were forced by ecological pressures away from their hideaway towards the coast, they may have interacted with modern humans. And if so, could competition, disease, or even predation then have been decisive factors?
Whatever the ultimate cause, our study provides the framework for future studies to examine the extinction of the iconic _H. floresiensis_ in the context of major climate change.
The underlying role of freshwater availability in the demise of one of our human cousins reminds us that humanity's history is a fragile experiment in survival, and how shifting rainfall patterns can have profound impacts.
_Nick Scroxton, Research Fellow, Palaeoclimate, National University of Ireland Maynooth; Gerrit (Gert) van den Bergh, Researcher in Palaeontology, University of Wollongong; Michael Gagan, Honorary Professor, Palaeoclimate, University of Wollongong; The University of Queensland, and Mika Rizki Puspaningrum, Researcher in Palaeontology, Bandung Institute of Technology, Institut Teknologi Bandung_
**This article is republished fromThe Conversation under a Creative Commons license. Read the original article.** https://www.sciencealert.com/where-did-indonesias-hobbits-go-study-reveals-major-new-clues
