"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, and die gallantly. Specialization is for insects." (Robert Heinlein)
Or to put it more bluntly:
"Single-mindedness is all very well in cows or baboons; in an animal claiming to belong to the same species as Shakespeare it is simply disgraceful." (Aldous Huxley)
What was it about the Renaissance that created men such as da Vinci, Michelangelo and Galileo? The printing press created a relative explosion in the availability of the printed word, and with it the lifeblood of learning: knowledge. The influx of Islamic learning (which also reintroduced a lot of Ancient Greek and Roman scholarship that had been preserved by Arabic scholars whilst the Europeans were busily destroying anything "heretical" during the Dark Ages) gave new ideas and avenues of exploration. The Church, which over the preceding centuries had become dogmatic and corrupt, was (slowly) losing its authority both spiritual and temporal; in the middle of the Renaissance Martin Luther wrote his 95 theses about the corruption of Church indulgences and began a process that would cleave the Roman Catholic Church in two. These events came together to provide an environment where not only was it becoming easier to find knowledge to learn from, but the overwhelming authority of the day was losing it's ability and authority to prevent people challenging the prevailing dogma. People could start to challenge the orthodoxy of how the world worked rather than having to be content with a religious explanation that had undertones of disapproval for your temerity in even asking the question.
It's said that da Vinci was the last man to know everything that could be known (although many others have jostled for this title), partly as a sign of his brilliance, but also as a sign of how much more there is to know nowadays. And that body of knowledge is expanding exponentially; whilst for da Vinci there was philosophy (the "natural sciences"), mathematics and art to master, for the modern human it would take a lifetime to become merely conversant with every branch of engineering, let alone a master of them. And then there is mathematics, physics, chemistry, biology, astronomy, psychology and so on and so on, and knowledge and understanding in all of these fields is increasing every day.
But the spirit of intense curiosity that drove the Renaissance men is no more abated today than it was then. And like the Renaissance men we are living in a time when knowledge and learning is undergoing an explosion of democratisation and availability, except this time it's the electronically printed word delivered through the internet rather than ink on a pig skin or dried wood pulp. We may no longer have the capacity to know the full corpus of human knowledge, but we can choose to learn anything that we wish, largely for free, from the comfort of our homes.
I've made the point before that the unicorn at the heart of scrum is the multi-functional team: very desirable but largely mythical. It's largely mythical for the simple reason that it's too difficult for a person to become a master of analysis and development and testing and documentation. It's not difficult because each of the individual elements is too difficult, but because they are all different skills with different pre-requisites and ever-increasing bodies of knowledge that you need to stay on top of to maintain your mastery. There simply aren't enough hours in the day, assuming you have some form of personal life (and would like, in no particular order, food, recreation, relationships and sleep). I stand by this, whilst accepting that there are a few people who can master 2 of these concurrently, and very, very occasionally 3 or more. For us mere mortals though, it's unrealistic to expect to be a 10x or full-stack developer whilst also having an encyclopedic knowledge of BABOK.
Nonetheless, that insatiable curiosity and thirst for learning that drove the Renaissance men to heights of mastery can and should be an inspiration to show that it is possible to have great knowledge in diverse areas. There is much overlap between the functions of each profession that makes up a scrum team; if da Vinci can be both a master anatomist and the inventor of the helicopter, is it beyond the bounds of reason that a single person could be both a master of documentation AND a competent tester, or a mistress of development AND a competent analyst, or any other combination of professions in your team? At the very least a database developer should also know the basics of web development; a technical writer should be able to write both API documentation and a Beginner's Guide and so on.
The march of the specialist has benefits for efficiency and productivity, but only the generalists can create things in a non-linear (non-conveyor belt) fashion, only generalists can see the bigger picture, anticipate how their work will affect others in their team and create and innovate within that team. Without expecting people to master multiple professions, there is still scope for learning things that other professions do every day, even if mastery is beyond you.
As with the Renaissance men it is no longer acceptable to say "I don't do that, I'm a developer/tester/analyst/technical writer." You can, should and must be more.