Once upon a Hobbit - The Fossil Chronicles - page 76

wanted to find out who. It is a good bet that Homo floresiensis 's ancestor
made the older tools . 8
But what did that ancestor look like? Was it small like Homo floresiensis
or considerably larger like Homo erectus, the only other known hominin
in the region, who had been living a couple of islands to the west (on
Java) when those first tools were flaked on Flores? At first, the discov-
erers thought that Homo erectus may have been Hobbit's ancestor, even
though body size had generally increased, not decreased, during hom-
inin evolution. After all, island-dwelling animals are known to evolve
in unusual ways. Once they settle on islands, over time certain large-
bodied species of mammals become dwarfed, whereas some smaller
species grow to gigantic proportions. Although this has happened on
islands everywhere, the so-called island rule 9 is somewhat misnamed,
because it does not apply to all mammals. Mice and certain rodents
have tended to become larger on islands, but equally small squirrels,
bats, and shrews have not . 10 Similarly, only some of the large mammals,
such as deer and elephants, have evolved a smaller stature on islands.
Around 900,000 years ago, a massive volcanic eruption eliminated
much of the animal life on Flores, including a species of giant tortoise
and a very small-bodied stegodont. Giant Komodo dragons survived
the event, however, and inhabit the island today, although in greatly
reduced numbers. Not long after the eruption, a few terrestrial animals
managed to reach the island, probably as passengers on uprooted trees
or other floating debris during tsunamis and violent storms or, in the
case of stegodonts, by swimming. Among these were a medium-to-
large stegodont, a rat, and, as indicated by their tools, the presumed
ancestor of Homo floresiensis . 11 After that, no other mammals successfully
colonized Flores until another volcanic eruption created empty niches
around 17,000 years ago. ( Homo sapiens arrived around 11,000 years ago.)
The mammals that settled on Flores soon after the volcanic eruption
900,000 years ago, thus, gave rise to those found in the fossil record
before the more recent eruption . 12 As is common under these circum-
stances, the smaller-bodied animals, such as rodents, proliferated into