I agree that the species concept is a bit of a mess but how do you conclude that these two populations can still interbreed?
From the article I do not get the same suspicion. Even though they mention the "sister species" is 1200km removed this might be true while being a "finished" allopatric speciation.
From the paper:
"Our fossil calibrated mitochondrial clock analysis estimates the most recent common ancestor of C. congoensis and C. satanas existed ~4.27–5.78 Ma. In an additional analysis that used the same secondary calibration point as Roos and Zinner [36], we obtained younger divergence estimates by approximately 1 million years (3.44–4.73 Ma)."
From the article I do not get the same suspicion. Even though they mention the "sister species" is 1200km removed this might be true while being a "finished" allopatric speciation.
From the paper:
"Our fossil calibrated mitochondrial clock analysis estimates the most recent common ancestor of C. congoensis and C. satanas existed ~4.27–5.78 Ma. In an additional analysis that used the same secondary calibration point as Roos and Zinner [36], we obtained younger divergence estimates by approximately 1 million years (3.44–4.73 Ma)."