Overview
I-L596 represents an upstream backbone segment within the I2b radiation and captures the earliest known structure ancestral to the better defined I2b1, I2b2 and I2b3 branches. In technical phylogenies, L596 and L415 mark a nodal point near the root of I2b, preceding the diversification into regionally focused western and central European clades. For atlas purposes, modeling I-L596 as a separate entry highlights the existence of a deep ancestral layer within I2b that is older than its better known downstream radiations.
This root segment likely emerged among late glacial or early postglacial foragers occupying western or central Europe. With time, most of its diversity was channeled into the branches that became I2b1, I2b2 and I2b3. However, a small number of lineages still sit close to this backbone and do not clearly fall into any of the more derived subclades, preserving an echo of the original I2b structure.
Geographic distribution
Backbone I-L596 lineages are rare in modern populations. When identified, they tend to occur at low frequencies in central and western Europe, including Germany, Switzerland, France and the Low Countries. Some individuals in the British Isles and Scandinavia also fall close to the L596 root, likely due to ancient connections through the North Sea and Rhine corridors.
Because most I2b derived lineages have drifted into downstream branches, the geographic interpretation of I-L596 must be cautious. Its distribution primarily indicates where rare, weakly differentiated I2b lineages survived rather than where the clade originally formed.
Ancient DNA
- A subset of Mesolithic and early Neolithic western and central European individuals show I2 markers that could represent very early I2b or I-L596 lineages, although coverage often prevents precise placement.
- The presence of I2b in multiple western and central European Mesolithic contexts supports the idea that L596 defined a deep ancestral node present in several refugial populations.
- Future high coverage sequencing of additional ancient samples is likely to refine the placement of basal I2b lineages relative to L596.
Phylogeny & subclades
I-L596 sits just above the major I2b1, I2b2 and I2b3 clades in the I2b tree. It serves as their common ancestor and delimits the point at which western and central European I2b radiations began to diverge from one another. A few modern lineages fall within this backbone category without clear downstream assignment, often due to incomplete marker coverage.
- I-L596* basal I2b backbone lineages
- upstream nodes ancestral to I2b1, I2b2 and I2b3
Notes & context
Including I-L596 as a root level segment for I2b underscores the fact that I2b represents an ancient radiation in its own right, rather than a small offshoot of other I2 branches. It helps users visualize the depth of the I2b lineage and its role in western and central European Mesolithic ancestry.
References & external links