'...when the various governments allowed embryos to be genetically modified beyond what was necessary to avert the Syndrome and other illnesses, they neglected to define the legal status of the resulting people. They just let the gemtechs get on with it.' [loc.2050]
Over a century ago, the incurable neurological Syndrome devastated humanity. A number of big companies (the 'gemtechs') developed genetic modification techniques that, applied at the pre-embryonic stage, imparted resistance. But the gemtechs didn't stop there: with the majority of a generation lost to the Syndrome, there was a huge demand for labour forces. And science is endlessly curious: what if we try this?
Hence, the gems: genetically-modified humans, often with distinctively neon hair or other visible signs of their status. Some are adapted to specific environments: others have been engineered to perform particular tasks. Many are socially (or psychologically) dysfunctional, valued for their abilities rather than their personalities. Are gems an artificial subspecies? Or are they less than human?
Gemsigns deals with the days before a major international conference at which these questions will be debated. There are multiple viewpoint characters, from Dr Eli Walker (genetic anthropologist: "I try to identify connections between human genetypes and behaviour"), to religous extremist John Senton, to Gaela, mother of the precociously gifted Gabriel. Gabriel, and Aryel Morningstar (a charismatic Gem activist whose Sign is not immediately apparent), drive the action of the novel: although many of the events don't affect them directly, their specific modifications (mutations?) are vital to the denouement.
The gemtechs have a vested interest in maintaining the status quo. They hark back to the 'good old days' when gems were intellectual property, with no rights at all. There's a lot of profit to be made in genetic modification: indeed, it seems to be the only area of science / technology where much progress is being made. In media and communication, for instance, 'socialstreaming' and something very like the internet are still going strong. So is the Observer. On the other hand, one theory has it that the Syndrome was caused by '[exposure] not only to a plethora of computing and communications devices, but to the immense load of interactions, analysis and responses they demanded, and the radio frequencies over which they travelled'. [loc.635] Advances in digital culture might be counterproductive.
There's a lot of worldbuilding here, and it's delightfully complex. That means there's the occasional infodump, and some of the essential background information is conveyed as reportage rather than narrative. But it's seldom intrusive, and serves to maintain an air of impartial omniscience.
Plenty of Big Themes here: slavery, surrogacy, the ethics and techniques of genetic modification, the obligations of society towards its weaker members, the nature / nurture debate, the future of London, the future of religion. Saulter deals with them provocatively and maturely. I'm looking forward to the next in the series.