Discover How a Rare Ancestor Uncovers the Journey of Giant Flightless Birds to Distant Lands

Ostriches, emus, rheas, and other large, flightless birds are spread across several continents, yet their journey to these far-flung places remains a mystery. One long-standing idea is that their ancestors walked to these locations when the Earth was one giant landmass known as Pangaea, existing over 200 million years ago. As Pangaea split apart, those ancestors were already in place.

However, recent studies challenge this idea. Genetic research shows that the last common ancestor of these birds lived around 79.6 million years ago and diversified between 70 and 62 million years ago. This timeline doesn’t align with the age of Pangaea’s breakup, so researchers needed to dig deeper.

Klara Widrig, a vertebrate zoologist at the Smithsonian National Museum of Natural History, and her team studied an ancient bird called Lithornis promiscuous, which lived around 59 to 56 million years ago. This well-preserved fossil provides a glimpse into the past of paleognaths, the group that includes today’s flightless birds. Widrig noted, “While we can’t be sure that Lithornis is the direct ancestor of modern paleognaths, it resembles what we think they looked like.”

Previous research indicated that another related bird, Calciavis grandei, might have flown, but there wasn’t enough data on bone structure to clarify how well it could fly. In a recent study, Widrig’s team compared the breastbone of L. promiscuous with those of living birds using 3D analysis. They found that its sternum shape matched birds capable of long-distance flight, like egrets and herons.

Peter Hosner, a curator of birds at the Natural History Museum of Denmark, explained that migratory birds are the exception, with most species staying close to their habitats. This suggests that ancient paleognaths could have flown to distant landmasses, where they evolved into the various flightless species we know today.

Around 60 species of paleognaths exist today. Most are resident birds that rely on ground foraging. For a bird to lose its flight, it typically needs two conditions: a plentiful supply of food on the ground and a lack of predators. This often occurs in isolated environments, like islands, but after the catastrophic Cretaceous-Paleogene extinction event 66 million years ago, many habitats became predator-free.

“Flight is hard work,” Widrig remarked, explaining that flightless birds could thrive in such settings. As predators reappeared, these birds evolved in response—some became large and intimidating, like the cassowary, while others developed speed, like ostriches.

Ultimately, despite their convergent evolution, these changes occurred independently, without any coordination among the species. Each adapted uniquely to its environment.

In today’s world, understanding how these birds evolved helps not only in studying paleontology but also in addressing modern conservation efforts. Flightless birds continue to face threats from habitat destruction and invasive species, making insights into their past crucial for their future.

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