Ancient Fig Wasp that Predates Fig Baffles Scientists

The discovery of a fossilized wasp species with an appendage remarkably similar to that of more recent wasps known for laying eggs in figs has puzzled researchers because figs did not come to exist until 65 million years after the fossilized wasp was alive.

The 115-million-year-old fossil specimen's ovipositor - the organ through which it lays eggs - is nearly identical to ones found on modern parasitic wasps known for laying their eggs on fig fruits.

The wasp fossil was discovered in northeastern Brazil and is considered to be a part of the Hymenoptera superfamily known as Chalcidoidea, a group that included about 22,000 known species out of an estimated 500,000.

"This is a tiny parasitic wasp, it's the smallest fossil wasp found in this particular deposit and it's the oldest representative of its family," said Sam Heads, a paleoentomologist at the Illinois Natural History Survey at the University of Illinois. "More importantly, it's possible that this wasp was fig-associated, which is interesting because it's Early Cretaceous, about 115 to 120 million years old. That's a good 65 million years or so prior to the first occurrence of figs in the fossil record."

Heads, who published the findings with colleagues in the journal Cretaceous Research, said the research demonstrates the value of studying insect fossils.

"The fossil record of insects is very extensive both geographically and temporally. It goes back 415 to 420 million years and preserves the ancestral forms of a lot of the insects that are alive today," he said. "So it's a great resource for understanding insect evolutionary history and the distribution of insects across the planet in the past."

Heads was quick to note that a wasp with an ovipositor that's similar to those of modern wasps that are known to lay their eggs in figs is not indicative of figs being present earlier than believed.

"There is no evidence of the existence of figs at this time and the most recent molecular study doesn't place figs that far back," he said, adding that while figs may not have been around, something like a fig could have been in existence and the wasp may have laid its eggs in the similar fruit. This would be an example of a phenomenon known as convergent evolution, Heads said, noting the occurrence of separate species independently evolving similar traits.

Another possibility is that the fossilized wasp is an early ancestor of the of the fig wasp, which would indicate that the fig wasps' ovipositor was around long before the fig wasp itself and that the insects later evolved to lay eggs in figs.

While the study of fossilized insects is not as illustrious as studying other fossilized creatures, such as dinosaurs, Heads notes the modern-day implications to be had in doing so, noting that information gleaned from studying ancient insects can be directly applied to existing knowledge of insects living today.

"When you talk about paleontology to people the first thing they think of is dinosaurs," he said. "And that's great. Dinosaurs are really exciting, wonderful animals. But for the most part, they're extinct. With insects and other arthropods like spiders and scorpions, they're around still. So we have modern forms to compare our fossil forms to, which is incredibly useful."