Just a few weeks ago I had a discussion with someone who was arguing that projected gender roles have little to do with the different types of careers that men and women have, because women are genetically inclined to nurture (and are better at nurturing than men). He brought up an article* that argued that male and female monkeys prefer different toys, which would support his belief that boys and girls play with different types of toys because of genetics.
In general, I know very little about gender toy preferences. I just know that I was never interested in dolls or other "feminine" toys. I also know that I was quite happy when my mom sent me off to college with a set of tools with flower decorations on them. I thought the decorations were amusing, but overall I just thought it was cool that I had a set of tools and most of the other girls did not.
For the people who dislike the idea of engineering toys for boys and engineering toys for girls, I think that at this point in time it is probably useful to have engineering/science toys clearly announce that they can be for girls. It is unfortunate that this is usually done by making the toy pink, but that seems like a separate problem that affects all types of toys.
*Here is the article: http://www.psychologytoday.com/blog/the-scientific-fundamentalist/200804/why-do-boys-and-girls-prefer-different-toys and some points about it based on what I have read ...
Regarding the Alexander/Hines study in the Psychology Today link:
(1) The researchers did not do a preference test which would have involved presenting all six toys at the same time. Instead, they placed a toy in the cage for five minutes at a time and filmed the interactions. Those interactions were then rated.
(2) The male vervets did not appear to prefer masculine toys over feminine toys.
(3) Female ververts preferred the feminine toys (mostly the pot) over the masculine toys.
(4) Both male and female vervets spent more time with the pot than with the doll.
(5) The authors hypothesize that the color of the pot (red) " may be signalling opportunities for nurturance and thus eliciting female responsiveness".
The Hassett/Siebert/Wallen study actually showed that male rhesus monkeys showed significant gendered toy preference but the females did not show a statistically significant preference (opposite the other study).