Accretion model of Neanderthal origins
In Palaeoanthropology, the accretion model is a theory for the appearance of Neanderthals. It suggests that those traits characteristically Neanderthal appeared gradually (accreted) over hundreds of thousands of years, rather than abruptly. First proposed by Piveteau (1970), it was developed by Vandermeersch (1978) and Jean-Jacques Hublin (1982, 1986, 1998, 2009a,b).
The model proposes four descriptive stages for the appearance of Neanderthal characteristics. According to those that defined the stages, these likely just reflect the discontinuity of the fossil record. For example, no specimen dates to OIS 8 (300-243 ka), so this gap serves to separate stages 2 and 3.
To 424 ka
Petralona
(right, male)
424 – 300 ka
Incipient occipital bun.
Increased occipital plane convexity.
Incipient to well-defined suprainiac fossa.
Steinheim 1
(right, female)
243 – 71 ka
Pronounced occipital plane convexity.
Elongated skull in the front-back direction.
Krapina 3
(right, female) Shanidar 2 and 4
71 – 40 ka
Nose cavity becomes larger.
Exaggerated occipital plane convexity.
Exaggerated suprainiac fossa.
Pronounced mid-facial prognathism.
Gibraltar 1
(right, female)
...
Wikipedia