Homo floresiensis was of tiny stature, about 1.0 metre tall, with a brain the size of an orange.  After prolonged initial controversy, the scientific community accepted it as a new hominin species and a cousin species to modern Homo sapiens.  H. floresiensis lived in Liang Bua Cave from about 190,000 to 60,000 BP, but further research by Morwood’s team excavating sites in the So’a Basin of Flores eventually discovered ancestral H. floresiensis remains dating to about 700,000 BP and stone tools that must have been made by these hominins dating to about 1.0 million years ago.

The evolutionary origins of H. floresiensis are still debated, but the most parsimonious explanation is that the hominin descended from a population of Homo erectus—well-documented on the island of Java to the west—made its way to Flores by 1.0 million years ago and became isolated.  Once on the island, the well-known selective forces on isolated land masses, known as the ‘island rule’, began to take effect, and the hominin’s body (about the same average size as a modern adult H. sapien) began to shrink, reaching its diminutive stature by 500,000 BP and evolving into a distinct species.  An alternative hypothesis is that the colonising hominin was not H. erectus, but was instead a smaller and evolutionarily more primitive hominin species (an australopithecine or Homo habilis) that somehow walked from Africa to Flores without leaving archaeological evidence in between.  In this scenario, it too was subjected to the island rule, leading to dramatic changes to body shape, but less radical changes in size.

Landing on Flores from a jumping-off point on Java or Sulawesi meant that Homo erectus was leaving behind familiar mainland Asian plants and animals to confront on Flores an exotic and unfamiliar mix of species.  Flores was populated by Komodo dragons, giant storks and rats, white-headed vultures, crocodiles, giant tortoises, and small endemic elephants called stegodon.  An often-overlooked aspect to this story is that these colonising hominins were able to take on and survive the challenges of Flores for over 900,000 years because they had an ‘ace in the hole’: the technological adaptation provided by stone tools.  The global history of our genus Homo shows that technology is an unparalleled means for squeezing the maximum amount of energy possible from the environment.

The stone tools made by H. floresiensis, first described by MoST Director Mark Moore—the stone tool analyst for Morwood’s research team—are technologically similar to Oldowan Industry stone tools from Africa.  Volcanic cobbles were reduced into flakes, which were the principal tool of these hominins.  Cores were reduced bifacially and frequently rotated, resulting in multiplatform and bifacial ‘centripetal’ cores.  Sometimes larger flakes were themselves flaked to produce more sharp-edged flakes, particularly in Liang Bua Cave.  Flakes were also retouched to shape the edges or resharpen them, and a perforator-like projection occurs on some retouched flakes and cobbles.  Some flakes and cores were placed on an anvil and smashed, truncating them into splinters with right-angled tool edges.  The bipolar technique was known to H. floresiensis, but most flaking was done by expert hard-hammer direct percussion.  Despite being the size of a modern human five-year-old, these hominins were able to remove well-struck flakes measuring up to 12 centimetres long from very tough volcanic stones.

There are some profound lessons to learn from the Flores story.  First, while stone-tool technology ensured the population’s survival for some 50,000 generations, it could not buffer our hominin cousins from the extremes of the selective pressures encountered on Flores.  Their skeletal anatomy and body shape morphed and natural selection profoundly affected their posture, the way they walked and ran, and the movement of their arms.  Even more significantly, their cranial capacity decreased to become on-par with a modern chimpanzee’s.  Yet Homo floresiensis didn’t lose the capacity to make stone tools. Their brains reorganised to retain the complex cognitive abilities necessary to make and use their toolkit, and the dramatic changes in body shape must have accommodated the physical requirements of forceful stone-flaking.  The hominin’s technological ability was crucial to the survival of these enigmatic creatures, but it could not break them free from the strictures of the island rule.

The H. floresiensis story, told through their stone tools, may be a lesson for all of us. Technology may be essential for survival, but it does not serve as a firewall against the powerful forces of natural selection.