1.   But a few scientists have proposed similar ideas, pointing out that all previous members of the early human ancestral line have had molars with increasingly thick enamel.

2.   Groth dismissed a long-held theory that the diversity of North American red crossbills was due to multiple invasions of different ancestral lines from Asia.

3.   In that case, it might even be a more direct ancestral line leading to modern humans.

4.   They also cast most australopithecines out of the human ancestral line.

5.   This ability has long been one of the defining characteristics of the human ancestral line.

6.   Though Yamaha says the new model is already back-ordered, its ancestral line has been troubled by its changing ecological niche.