An article published in the journal “Communications Earth & Environment” reports a study that offers a possible explanation for the extinction of the species Homo floresiensis (Photo of the individual cataloged as LB1 by Mamoritai), the hominins whose fossil remains were discovered on the Indonesian island of Flores. A team of researchers has found what they believe is evidence that climate change began approximately 61,000 years ago, leading to millennia of drought. The Homo floresiensis population and the pygmy elephant that inhabited Flores at the time were affected by that drought, which may have led to their extinction.
In the twenty years since the discovery of the first remains of Homo floresiensis, nicknamed “hobbits” due to their small stature, many researchers have attempted to reconstruct the history of these hominins. The conditions in the Liang Bua Cave made dating the remains difficult, and several tests provided results that are expected to be increasingly precise. This new study is based on dating the various remains between 100,000 and 60,000 years ago.
Understanding the evolution of the climate on the island of Flores requires specific geochemical analyses. In this case, in a cave called Liang Luar, about 700 meters from Liang Bua, the researchers luckily found a stalagmite that grew during the time Homo floresiensis lived on the island. Stalagmites grow layer by layer, so a geochemical analysis can be of great value in reconstructing climate changes in the area.
Two analyses were conducted on the stalagmite in Liang Luar Cave. One is known as delta-O-18 and is used to measure the ratio of stable oxygen isotopes: oxygen-18 and oxygen-16, which indicates changes in monsoon strength. The other is used to measure the ratio of magnesium to calcium, which indicates the total amount of rainfall.
The analysis of the data obtained indicates that the island of Flores experienced three climate phases in the span of less than 50,000 years. Between 91,000 and 76,000 years ago, the climate was wetter than today. Between 76,000 and 61,000 years ago, the monsoon was seasonal, resulting in rainy summers and dry winters. Between 61,000 and 47,000 years ago, the climate became much drier in summer.
The next phase of this study was conducted by examining the enamel of a tooth from Stegodon florensis insularis, the pygmy elephant that lived on the island of Flores and was a prey item for Homo floresiensis. Again, delta-O-18 analysis was used, and the results confirmed the stalagmite analysis. This indicates that 90% of the pygmy elephant remains discovered date back to a period between 76,000 and 61,000 years ago, during the most favorable climatic period for this species. As the climate became drier, both these pygmy elephants and Homo florensis almost disappeared.
According to the researchers, it’s possible that the Wae Racang River, which once flowed through the area, shrank and the pygmy elephants moved to another area in search of freshwater. Homo floresiensis may have followed their prey, which was a key food source.
The excavations also revealed that the most recent fossils of Homo floresiensis and pygmy elephants were covered by a thick layer of volcanic ash dating back approximately 50,000 years. It’s possible that a volcanic eruption made the climate situation worse, leading to the extinction of these two species.
It’s still unclear whether Homo floresiensis ever encountered Homo sapiens. The first archaeological traces of modern humans on the Indonesian islands date back 60,000 years, so it’s possible that some of them arrived on the island of Flores but left no traces. Competition between different human species is always taken into account when researchers study the possible causes of the disappearance of a hominin species, so it would be useful to know if Homo sapiens reached Flores when Homo floresiensis were still present.
This study offers very interesting conclusions regarding the influence that changes in environmental conditions can have on an ecosystem. There’s debate regarding the level of intelligence of Homo floresiensis, a key factor in understanding their ability to adapt to such changes. Looking at the behavior of their modern cousins, it’s not difficult to understand why climate change could have caused their extinction.
