Assistant Professor Chris Reinhard is the lead author on the study:  False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth, published in the Journal Astrobiology.

Inside Science has an article on the paper by Ramin Skibba.  Here in an excerpt:

To a distant observer peering through a telescope, even Earth would not have shown signs of life through most of its past. Despite the fact that our planet was teeming with mostly microscopic life for three billion years, levels of oxygen and methane -- gases often produced by metabolizing organisms -- would have been too low to be noticed from afar. This means that today's scientists on Earth might not be able to detect commonly assumed signs of extraterrestrial life, and they might give up on planets that are actually inhabited, according to a new study in the journal Astrobiology.

“There are huge swaths of time throughout Earth’s history during which it would’ve been difficult to see the presence of these metabolisms even though we know from the rock record that they were around. It’s a sobering thing,” said Christopher Reinhard, an Earth scientist at the Georgia Institute of Technology in Atlanta, and lead author of the study, who presented the research at a conference in Mesa, Arizona on April 27.

Bio

Dr. Chris Reinhard’s background is originally in evolutionary biology, but his past and current research is best characterized as falling under the label of 'deep time biogeochemistry' — He is fascinated and astonished by the observation that our planet has come to support a pervasive biosphere, and seek to reconstruct how we got here. This involves combining techniques from aqueous geochemistry, geology, and biogeochemical modeling in an effort to reconstruct Earth surface environments as they have changed over long timescales through Earth's deep history and how this evolution has been coupled with the evolution of microbial and macroscopic life. He received his Ph.D. in Earth Sciences from the University of California, Riverside in 2012 and joined Georgia Tech as an Assistant Professor in 2014.