Over the last five years, astonishing advances in ancient-DNA analysis have provided remarkable insight into Neanderthal genetics. As a result, the evolutionary connection between humans and Neanderthals has been severed. In other words, evolutionary biologists no longer think of Neanderthals as a transitional species linking the primitive bipedal primates, such as Homo erectus, to modern humans.
This stunning conclusion comes from analysis of mitochondrial DNA recovered and sequenced from Neanderthal remains.1 DNA sequencing refers to the process of determining the exact order of the chemical building blocks (bases A, T, C, and G) that comprise DNA strands. The average percent and locations of the differences between Neanderthal and human DNA sequences indicate that Neanderthals did not evolve into humans.
Researchers conducted the first studies on three distinct specimens that date between 30,000 and possibly 100,000 years in age, from three locations in the Neanderthal’s range (Germany, Russia, and Croatia). The DNA sequences obtained for all three Neanderthal specimens display remarkable agreement with one another. In fact, the DNA sequences vary by only about 3.7%. This sequence diversity compares favorably to that measured for modern humans (3.4%). Such similarity within the species, but dissimilarity between the species, indicates that these animals did not make any genetic (hence, evolutionary) contribution to modern humans.
More recently, scientists have isolated, amplified, and sequenced mitochondrial DNA for two more Neanderthal specimens. The specimens were recovered from new excavations of Feldhofer cave deposits—the location in the Neander Valley, Germany, where Neanderthal remains were first discovered.2 The DNA sequences of these two newly discovered specimens closely agree with those obtained for the three earlier studies and fall within the parameters for Neanderthal genetic diversity.
Ancient-DNA analysis makes many scientists uneasy, since contamination can readily creep in during the isolation and amplification processes. This wariness, however, can be confidently dispelled for the Neanderthal mitochondrial DNA sequences since independent research teams have generated consistent results for five different specimens. The conclusion is undeniable: Neanderthals did not give rise to modern humans.
References:
Matthias Krings et al., “Neanderthal DNA Sequences and the Origin of Modern Humans,” Cell 90 (1997): 19-30; Matthias Krings et al., “DNA Sequence of the Mitochondrial Hypervariable Region II from the Neanderthal Type Specimen,” Proceedings of the National Academy of Sciences, USA 96 (1999): 5581-85; Igor V. Ovchinnikov et al., “Molecular Analysis of Neanderthal DNA from the Northern Caucasus,” Nature 404 (2000): 490-93; Matthias Krings et al., “A View of Neanderthal Genetic Diversity,” Nature Genetics 26 (2000): 144-46.
Ralf W. Schmitz et al., “The Neanderthal Type Site Revisited: Interdisciplinary Investigations of Skeletal Remains from the Neander Valley, Germany,” Proceedings of the National Academy of Sciences, USA 99 (2002): 13342-47.
