As tokenadult points out, these studies are serious business. Anecdata doesn't really cut it.
How do you explain savants/prodigies?
We are all born differently. Our brains work different ways. Our muscles want to do different things. As such we have a propensity towards one thing or another.
It is true if you have kids you can see this. Every single baby is completely different, even newborns, in how they respond to things.
We are, of course, all different. Diversity is a great strength. That doesn't mean that there's a biological basis for every kind of difference.
Also, even if it was, I'll take scientific evidence over 'belief' any day.
Not that I'm saying these type of studies are not useful.
It is, unsurprisingly, called "Regression to the Mean".
> Broad genetic influence on the five dimensions of Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness was estimated at 41%, 53%, 61%, 41%, and 44%, respectively.
Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas (2009). Beyond Heritability: Twin Studies in Behavioral Research. Current Directions in Psychological Science, 18, 4, 217-220
http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...
Indeed, there are psychologists who are fully aware of the research base on heritability of the "Big 5" personality dimensions you mention who nonetheless research interventions to change people's personality along one or more of those dimensions. It is already well known to personality researchers that personality changes over the course of life (from early childhood to old age) much more than most people think it does.
On the flip side, just because a feature isn't heritable, doesn't mean it can be changed through an environmental intervention. Many people assume that what isn't strictly genetic, must me malleable but there may be more than a fair bit of just randomness there or hard to alter circumstances (pre-natal environment, remnants of infections).
"Don't think that you can't do what other people can. And I agree you shouldn't underestimate your potential. People who've done great things tend to seem as if they were a race apart. And most biographies only exaggerate this illusion, partly due to the worshipful attitude biographers inevitably sink into, and partly because, knowing how the story ends, they can't help streamlining the plot till it seems like the subject's life was a matter of destiny, the mere unfolding of some innate genius. In fact I suspect if you had the sixteen year old Shakespeare or Einstein in school with you, they'd seem impressive, but not totally unlike your other friends.
"Which is an uncomfortable thought. If they were just like us, then they had to work very hard to do what they did. And that's one reason we like to believe in genius. It gives us an excuse for being lazy. If these guys were able to do what they did only because of some magic Shakespeareness or Einsteinness, then it's not our fault if we can't do something as good.
"I'm not saying there's no such thing as genius. But if you're trying to choose between two theories and one gives you an excuse for being lazy, the other one is probably right."
We are NOT sure, on the basis of research, what anyone's upper limit of ability is. We have no idea about the extent of the "reaction range" constrained by the shuffle of genes a person obtains before a person is born, but we are absolutely sure that the reaction range is a RANGE, exquisitely sensitive to environmental influences. The discordance of identical twins for all human behavioral characteristics amply proves that. So, yes, let's say determination can matter as much or more than inborn ability. There are ample examples of that in today's world.
EDIT AFTER SEEING stiff's COMMENT AT THIS LEVEL:
Yes, many children bail out of further study of mathematics because they assume school lessons should be easy, and so they think "they have no talent" for subjects that become hard. A series of FAQs I have written about mathematics learning,
"Problems versus Exercises"
http://www.epsiloncamp.org/ProblemsversusExercises.php
"Repetition and Practice"
http://www.epsiloncamp.org/RepetitionPractice.php
"Resources about Learning Mathematics"
http://www.epsiloncamp.org/LearningMathematics.php
"Courage in the Face of Stupidity"
http://www.epsiloncamp.org/CourageandStupidity.php
were written to encourage learners to be willing to challenge themselves when they feel stuck learning mathematics. Most professional mathematicians feel stuck a lot of the time when they do their daily research work, but they keep going.
As my dad always used to say, 50% is talent, 50% is effort. Someone with the 100% talent, who's a lazy fuck (50% overall) will be outperformed by far by someone with 50%/mediocre talent putting in 100% of work (75% overall).
Their personality might keep them from succeeding at learning (e.g. too lazy to read a book), but that doesn't mean they're mentally incapable of it.
There is certainly some inborn variation between people. Anyone with children is aware of it. Two children of the same parents can have very different personalities. So what exactly is it supposed to mean to "eliminate a belief" in variation in inborn ability? That we're supposed to believe something that's not true? That seems a bad road to go down. Not just because it's unwise to base your ideas on lies, but also because you won't convince anyone smart with an ideology based on a premise so obviously false.
Better just to say that determination can matter as much or more than inborn ability. That works just as well and has the added advantage of being true.