The beginning is almost never the most compelling or important part. It's just the bit you thought of first, based on your subjective chronology.
Signposting what you're going to write about is good, but starting with an exhaustive list of definitions is extremely boring.
Invoking paleolithic people is an overplayed way to convince us your topic is cosmically important.
Openings need tension – paradoxes, unanswered questions, and unresolved action
Good openings propose problems, pose questions, drop you into an unfinished story, or point at fundamental tensions within a topic. Ideally within the first paragraph or two.
"Good writing starts strong. Not with a cliché ("Since the dawn of time"), not with a banality ("Recently, scholars have been increasingly concerned with the questions of..."), but with a contentful observation that provokes curiosity."A Sense of StyleStephen Pinker
Creating tension in non-fiction work is trickier because your story is (hopefully) constrained by reality. You are not at liberty to invent suspicious murders, salacious extramarital affairs, or newly-discovered-magical-powers to create tension and mystery. You have to deal with the plain, unexotic facts of the world.
Your job becomes much harder if you pick topics with no tension, problems, or puzzles within them. To paraphrase Williams, it is more of a failure to pose an uninteresting problem, than to poorly articulate an interesting one
Your interest in the topic is your best directional clue for finding the tension or interesting paradox. Your urge to write about the thing hopefully comes from a place of curiosity. You have unanswered questions about it. It feels important or consequential for unexplained reasons. You think you've seen things in it other people haven't. Pay attention to that interest.
Problems are a destabilising condition that has a cost for a community of readers that needs a solution. Destabilising condition is just a fancy word for “change” here – a change in the status quo. Put another way, a problem is an expected turn of events, that has undesireable consequences, for an audience who will care about it, that we want to explore solutions to.
Williams is speaking to a community of academic writers in his book. They're trying to present scientific and research problems in plain, objective language, which isn't necessarily what we want to do with narrative writing like blogging or personal essays.
We have a little more liberty to put interesting padding around the change, consequences, and solution, such as telling an opening anecdote, or drawing readers in with characters, rich details, and sensory descriptions.
Williams suggests we try to state our problem and then ask a series of so what?'s to get at the underlying problem
For your writing to be worth reading, you need to be exploring something of consequence for someone
When McPhee writes, after first immersing himself in his raw material (field notes, interview transcripts, official documents) for weeks, he then draws a structure for the work. The structure lays out the major themes and scenes he'll work through, in the order that will make them most compelling and coherent.
Developing a structure requires navigating the tension between chronology and theme. Chronology is what we default to, but themes that repeatedly appear want to pull themselves together into a single place. The themes that really matter should be in your opening. Even if the moment that best defines them happens right before the end of the timeline.