Animals have it easy.
For them, sex is all about eggs or pups or calves.
IN TOUCH: Send Your Video Comments
No animal has to commit to a relationship to lure the female of the species into the nest.
We humans are much more complicated. Women need to be in the mood, which many men don't seem to understand.
"I think that most men, and I have to underline the word 'most,' just don't get it," said Jenny McCarthy, an actress, former Playmate of the Year, and best-selling author of "Life Laughs: The Naked Truth about Motherhood, Marriage, and Moving On."
She laments that our differences -- the ones that can make sex so much fun -- can also get in the way.
"It's amazing to me how much brain work it takes for a girl to have an orgasm," McCarthy said. "Guys just need to look at a nipple, and they lose it. God, I wish it was that easy for us!"
That's just one of the differences between men and women that are explored in a new reality series, "Sexual Healing," on Showtime.
Sex therapist Laura Berman hosts it. She said those differences are stunning.
"First and foremost, men tell me they don't get enough sex. That's the biggest complaint," Berman said.
On the other hand, when she recently saw a married couple that hadn't had sex for years, the wife told Berman, "I'm kind of at the point where I could live the rest of my life and not have it again."
That's not unusual.
About 30 percent of women -- more than six times that of men -- have a low libido, or sex drive, studies show.
If it's physiological, there are remedies, such as hormone medication.
But there are other reasons a woman can't have sex just like a man.
"Women need a context in which to be sexual," Berman said. "She has to feel good about the situation, even about the surroundings, in order to let go and really enjoy the sexual scenario."
And a man?
"A man isn't as picky," Berman said. "It's just the way they're wired. Men are much more goal-oriented. And so they'll try to heat things up way too quickly. And if, you know, men are a microwave oven, women are a slow-cooking stove."
Women are also more easily distracted than men, even in bed.
McCarthy admitted that she often made lists -- grocery lists -- while making love.
"That's not because she's not interested. Women are natural multitaskers," Berman said. "Our main sexual organ is our brain. So our body can actually be physiologically responding, but if we're not in a state of mind to respond, it doesn't register."
There are solutions to this often inconvenient gender gap.
Berman said it's all about communication -- telling your partner what you like and what works.
McCarthy agrees, especially because, now divorced, she's found the right context for her love life with movie star Jim Carrey.
"It's very real, very loving, very spiritual," said McCarthy of her relationship with Carrey. "And the sex is beautiful."