Is that a challenge? 

Why not?

2 points

1)There are cues that women can pick up on to establish when they are fertile. Do they work for every woman, I don't know, but I know they worked for me and for plenty of other women. I got pregnant on the first try because I had been monitoring said cues.

2)There is a tendency of women living in close proximity to synchronize their cycles, I don't think that would help your chances of impregnating them at different times of the month. I don't know how far apart they need to be, or how much time spent apart to counter this.

If the goal here (and the driving force behind having multiple mates) is to spread your genetics as far and wide as possible, technology can accomplish things that no amount of real sex could!  Sowing your seed as broadly as possible now would have to come down to artificial insemination.

I read a story a few months ago about a doctor who was a regular sperm donor that now estimates he has 400+ (I believe that was the number) biological children out there thanks to a poorly regulated system.

There are downsides obviously, it's not natural, you don't get help around the house and you don't get the sex.  On the plus side you don't have to share the finances and the children aren't your responsibility!

Haha, can you imagine if several of his biological children unknowingly got married to each other and had kids? Inbreeding FTW! At least they'd only be half-siblings. Gross lol

On the plus side you don't have to share the finances and the children aren't your responsibility!

Yeah, about that,

http://www.post-gazette.com/pg/07130/784968-100.stm

http://news.bbc.co.uk/2/hi/uk_news/england/london/7125895.stm

although:
http://www.bizjournals.com/boston/stories/2009/09/28/daily44.html

Maybe a copy of 'Sex at Dawn'?  Get her to read the entire archives of Dan Savage?

I personally feel that humans vary enormously - and in doing so we would not be the only species where there exists different mating strategies within the same species.  Some people are naturally monogamous - either with several long-term partners (say 3-10 years each) or one person for a long time.  Some (most?) people are not and for a lot of people life-long monogamy is an unrealistic expectation.

It seems to me unlikely that most paleo couples would stay together for 20+ years.  Biologically and hormonally, 'love' fades after 2-5 years.  It makes sense for a paleo lady (or man) to spread her genetic bets and have her children with different men.  Also, people back then would have died suddenly via childbirth, hunting accident etc. 

Generally (GENERALLY!) speaking, of course women are more towards the monogamous than men - it's their biological imperative.
There are quite a lot of women who simply have no interest in or desire or understanding of casual sex - which is perfectly acceptable.  But it's these women who cannot understand that their partner may be able to sleep with another woman and not have it affect his feelings for her - because they could never do the equivalent.   And the best partners for such women, I guess, would be the men that are naturally monogamous and have no interest in extra-relationship sex (and they do exist).

 I think that in paleo times people would have been more 'polyamorous' than 'polygynous' - pair bonds for 1-5 years but extra-relationship sexual activity outside of that pairbond (like in many supposedly monogamous birds).  But I do also have a sneaking suspicion that some guys would have got nothing (c.f. oodar celibacy thread) and some guys would have had 2 or more ladies - and the reason that women do seem to be more sexually 'fluid' than men is because they may have been sharing the same guys. 

I was once watching a BBC documentary (I think it was tribal wives) were the older tribesmen had several wives, and the younger tibesmen had no wifes.  But, all the wifes had extra-martial boyfriends, usually the younger tribesmen!

Personally I have no interest in polygyny or marriage in general, but I have had in the past and will in the future, long-term 'open relationships'.  They are difficult and require absolute trust and total communication, but when they work are a beautiful thing.

 There is a big difference, I feel, between polyamory and polygyny.  The latter is inherently sexist and the woman involved are often subjugated/generally repressed and not equal partners in the relationship...more like possessions, and that I object to.

Polygamy is a marriage which includes more than two partners. In some states and countries, Polygamy is not accepted. The Browns, the polygamist household featured in the reality show “Sister Wives” has submitted a case against the state of Utah. The household is challenging bigamy statues that guard against polygamy. The suit requests an injunction against any criminal prosecution for polygamy, challenging that it violates their constitutional freedom. Polygamist family from Sister Wives show taking Utah to court.