Genetic map of the Habsburg Jaw - updated

The jaw, as seen in Rudolph II -

And the genetic map of the trait -

Interesting how it becomes more common as the generations continue to inbreed.  More details in this prior post, which featured this family tree for King Charles II of Spain:

Painting: Joseph Heintz the Elder: Emperor Rudolf II, c. 1592 © Kunsthistorisches Museum /Kunsthistorisches Museum Vienna.

Reposted from 2011 to add new information about the risks of breeding with first cousins.  We've all known since our childhoods that breeding with a close relative increases the risks for the emergence of a recessive disorder like CF, sickling, hemophilia, and Gaucher's.  But this new study finds other risks:

Researchers at the city's university are entering their 18th year of the Born in Bradford study. It's one of the biggest medical trials of its kind: between 2007 and 2010, researchers recruited more than 13,000 babies in the city and then followed them closely from childhood into adolescence and now into early adulthood. More than one in six children in the study have parents who are first cousins, mostly from Bradford's Pakistani community, making it among the world's most valuable studies of the health impacts of cousin marriage.

And in data published in the last few months - and analysed in an upcoming episode of BBC Radio 4's Born in Bradford series - the researchers found that first cousin-parentage may have wider consequences than previously thought.  

They found that even after factors like poverty were controlled for, a child of first cousins in Bradford had an 11% probability of being diagnosed with a speech and language problem, versus 7% for children whose parents are not related.

They also found a child of first cousins has a 54% chance of reaching a "good stage of development" (a government assessment given to all five year-olds in England), versus 64% for children whose parents are not related...

... it adds to a growing concern among scientists that has caught the attention of lawmakers across Europe. Two Scandinavian countries have now moved to outlaw cousin marriage entirely. In Norway, the practice became illegal last year; in Sweden, a ban will come into effect next year.

For most in the UK, the prospect of marrying a cousin is largely alien. But it wasn't always so unusual. The father of evolution Charles Darwin married his first cousin, Emma Wedgwood. Their son, the Victorian scientist Sir George Darwin, went on to estimate that cousin marriages accounted for almost one in 20 aristocratic unions in 19th Century Britain. One of them was Queen Victoria, who married her first cousin, Prince Albert. The novel Wuthering Heights is full of fictional examples...

But crucially, Prof Oddie thinks the main risk to genetic health in Bradford is not cousin marriage, but a similar issue known as endogamy, in which people marry members of their close community. In a tight-knit ethnic group, people are more likely to share common ancestors and genes - whether or not they are first cousins, he says.

Endogamy is not unique to Pakistani communities in the UK. It is an issue too in the UK's Jewish community and globally among the Amish and also French Canadians.

"It's often the case that the exact familial tie can't be traced, but the gene occurs more commonly within a certain group, and for that reason, both parents carry the affected gene," Prof Oddie says. "It's an oversimplification to say that cousin marriage is the root of all excess recessive disorders in Bradford or in Pakistani communities. Endogamy is an important feature."

Related:  "Mommy, what's an Icelandic incest-blocker?"