Like other paleontologists, Elga Mark-Kurik had long pondered that moment in geological time when the first ancestor to all land vertebrates, including man, stepped from the water and walked onto solid ground.
But the 71-year-old never imagined that a fossil of a possible species linking fish and land animals may have already been in her collection for more than 40 years.
At a recent forum at London's Natural History Museum, scientists said the 375-million-year-old jawbone Mark-Kurik found in 1953 and a similar fossil found in Latvia in 1964 could be the missing link between water and land animals.
Many scientists agree the 25,000 species of land vertebrates, including homo sapiens, all descend from a small group of creatures that were not yet quite land animals and no longer quite fish. But nobody had ever unearthed such evidence.
The most developed fish, whose fossils are relatively common, date back to about 385 million years; the earliest, clearly land-roving animals are some 365 million years old - leaving a gap of 20 million years between fish and land animals.
An article by Mark-Kurik and fellow paleontologists Per Ahlberg of Sweden and Ervins Luksevics of Latvia claims that the Baltic fossils fall within that gap. The article will be published in the August edition of the prestigious British journal Paleontology.
That one of paleontology's Holy Grails may have been discovered in Estonia and Latvia has been celebrated across the two former Soviet Baltic republics and at Tallinn's Institute of Geology where Mark-Kurik works.
Sitting in her office, she proudly pulled the thumb-sized fossil out of a small blue box and gleefully handed it to a reporter.
But she hastened to explain that thanks to repressive Moscow rule, which only ended with the collapse of the Soviet Union in 1991, it was a fossil find of a lifetime that was unnecessarily delayed.
"This has been very exciting for scientists here," said Mark-Kurik. "We had gone through such a long, dreadful period in the Soviet Union."
As a schoolgirl in 1941, a year after Soviet forces occupied the Baltic states, Mark-Kurik and her family hid in fear one night when KGB troops knocked on their door. She said they were lucky to escape deportation.
She also says it was isolation behind the Iron Curtain that kept her and other scientists from recognizing the importance of the fossil she found in an Estonian cave as a graduate student.
For decades, the Soviet regime kept her from traveling abroad to meet colleagues and see other fossil collections, and the KGB closely monitored the rare Western scientist who visited Estonia.
Scientific rules also generally required that research papers be written in Russian, so Western paleontologists couldn't readily glean insights from Mark-Kurik's published works.
"Paleontology is very much a world science," she said. "You must see fossils from around the world and you must exchange information with other scientists to understand what you have. We couldn't under the Soviets."
After the country regained independence in 1991, Mark-Kurik suddenly had the freedom but not the money to travel. She still shares an office the size of a walk-in closet with two other researchers and is paid less than 6,000 Estonian kroons - or dlrs 400 in U.S. currency - a month.
The turning point came in the mid-'90s, when Mark-Kurik, Ahlberg, Luksevics and a Russian scientist won a grant from NATO to compare ancient rocks and fauna from Scotland and the Baltics.
They weren't trying to find the link between fish and land animals. But Ahlberg had studied the field in depth and the pieces of the puzzle suddenly fell together during a routine look at the Baltic jawbone fossils.
Jaw bones have distinctive, complicated joints and undergo huge changes with evolution; by comparing and contrasting them with other better-known specimens, jaw bones are especially good at revealing traits ohis hands had just the right mix of fish and land-vertebrate features that he knew well from other fossil collections, and he understood their significance almost instantly.
"These (Baltic) fossils fall bang in the middle of the gap," he said.
The animal was dubbed Livonia multidentata in Latin after the region where the fossils were found and its unique, five rows of razor-sharp teeth.
"I haven't seen anything like it, with multiple rows of teeth," said Jenny Clack, a paleontologist at the University of Cambridge who was not connected to the find. "This find is certainly part of the story of the origin of tetrapods (early land animals). It's the latest twist."
But unanswered questions remain. One is whether it still had fins or already had legs. To find out, Ahlberg said the search will turn to unearthing a whole skeleton.
If it exists, it would likely be here in northern Europe, which, because of the earth's shifting tectonic plates, was at the equator and featured shallow, nutrient-rich tropical waters 400 million years ago.
But Mark-Kurik says chances of finding a full skeleton are slim.
That leaves paleontologists extrapolating how it looked by comparing Livonia multidentata to its nearest cousins, for which there are full skeletons: It probably looked like a small crocodile, though with gills and a fish-like tail.
She herself hardly seems enamored with what could have been man's first terrestrial forefather.
"It must have been horribly ugly ... I wouldn't want it walking around my house," she said.