Can a baby look like someone whos not the father?

If you were to spend time in a maternity ward listening to proud new parents, you’d definitely hear them discussing their offspring’s genetic heritage. Does the new baby have her eyes or his? Could that be great Uncle Charlie’s nose? What you won’t often witness is the father turning tenderly to the mother and murmuring, “Hey, he looks just like Phil! You know, your ex? With the motorbike, and sociopathic tendencies?” But new research suggests that this scenario is more plausible than it sounds.

It has been shown that newborns may resemble a mother’s previous sexual partner, after scientists at the University of South Wales observed an instance of telegony – physical traits of previous sexual partners being passed down to future children.

The researchers found that, for fruit flies, the size of the offspring matched the size of the first male the mother mated with – not its biological father. It is thought that molecules of the semen produced by the first partner might be absorbed by the mother’s immature eggs.

“We don’t know yet whether this applies to other species,” explains author of the study, Dr Angela Crean. Too late, Dr Crean! I’m already working my way through a mental Powerpoint presentation of my exes and trying to work out whether I can travel back in time with a box of Durex.

The idea of our unborn children resembling partners past might initially fill us with horror, no matter how amicably your relationship ended. Your ex is not supposed to lurk inside you, waiting to burst forth in miniature form. This idea is scarier than Alien.

I’m sure plenty of prospective mothers feel incredibly guilty about the fact that they might be, unwittingly, about to fill the world with children who blow their nose on their sleeves, claim they have a moral objection to booking restaurants, and pronounce the eighth letter of the alphabet “haitch”.

However, if the hypothesis holds, it might not be entirely bad news. Whether we like it or not, the people we choose to date, and sleep with, reflect something of ourselves. It’s easy to write off past relationships in the same way we shudder at old pictures in which you’re wearing embellished, stonewashed denim. “Past me was such an idiot!” I often think. “I’m much wiser now.” But we ought to give our old selves more credit for doing what seemed right at the time – or at least acknowledge the fact that every decision which feels right now could seem just as foolish in five years.

If your children do share some traits with your former partners, it probably only shows the way that you were previously nurtured affects their nature. You’re human, and just as you’ll face difficult choices and make mistakes after they’re born, the way you behaved before they were born could impact on them too. Essentially, you have to accept that your old partners had admirable qualities which drew you to them in the first place, and that you’d be happy to pass them on to a child - or you have to admit that your current partner might also have bad qualities, and you’d be better off if you didn’t have children with anyone.

Despite the fact there’s still no solid evidence that the study applies to human reproduction, small children and exes can be equally irritating. You might, sleep deprived and frazzled, look at the freshly bathed toddler who has just started to massage their scalp with spaghetti hoops and think, “My ex used to make me feel this weepy and panicky! This must be his baby!” – when they don’t really have anything in common, just that your former partner used to act like a big baby and your infant child actually is one.

Ultimately, it’s down to you to teach your child to be a responsible citizen and happy human being. You may not have had the power to change your ex’s worst habits, but if the theory of telegony is true, you can find some satisfaction in taking control of the way their descendants behave.

When you're pregnant, it's fun to speculate about your future baby's appearance. What will their hair look like? Will they have blue eyes or brown eyes? But while parents can't help but make predictions, they can never be 100% sure until after the baby actually arrives. "If we examined all a fetus' DNA, we still wouldn't be able to truly anticipate things," says Barry Starr, Ph.D., geneticist in residence at The Tech Museum, in San Jose, California. "So much is unknown about genes."

Still, scientists do have some understanding about why people develop the features they do. Here's everything parents need to know about what their baby might look like.

What Will Your Baby's Hair Look Like?

Individual people inherit multiple gene pairs that play a role in determining hair color (and each pair includes one gene from each parent). If a baby inherits 10 pairs of genes in all, for example, that means 20 different genes could affect their tresses, says Michael Begleiter, a genetic counselor at Children's Mercy Hospitals and Clinics in Kansas City, Missouri.

But scientists haven't yet determined how many genes ultimately decide someone's hair color. If two brunette parents produce a blonde baby, that means both parents carry recessive blonde genes among their dominant brown ones, but only their light-colored genes were passed on. "When sperm met egg, the right mix of genes popped up so it could be expressed," says Dr. Starr.

The genes that set hair color (as well as eye color and complexion) also regulate a person's melanocytes, or color-producing cells. Where a baby's hair color will fall on the spectrum from black to brown, or red to blonde, may be determined by how many melanocytes they have, how much of each shade they churn out, and what pigment those make (one type, eumelanin, produces black to brown; the other, pheomelanin, makes yellow to red).

The more color-producing cells a child has, and the more eumelanin those cells make, the darker their hair will be. If they have relatively few melanocytes that mostly manufacture eumelanin, you can expect light brown or blonde hair. And the more pheomelanin their cells produce, the redder their hair will be.

Of course, hair color isn't necessarily stable over time. A child's hair may undergo changes as they age, especially as they hit puberty when hormones can activate genes that cause it to darken or curl.

What Will Your Baby's Eyes Look Like?

Some babies are born with bluish-gray eyes, but that can change as they grow. In fact, unless a baby's eyes are very dark at birth, they will typically change. And it can take at least six months before an infant's eye color stabilizes. "The color-producing cells in the iris need exposure to light to activate," says Dr. Starr.

At least two genes influence the eye shade that develops, and each can come in two forms, or alleles: one that has brown and blue versions, and one that has green and blue versions. A baby's eye color will depend on the combination of alleles they inherit from each parent.

If one parent has dark eyes and their partner's are light, the baby is likely to end up with dark eyes as well. That's because the brown allele is dominant, so if a baby gets one, they'll develop brown eyes. Still, even two brown-eyed parents can produce a light-eyed child if they both carry recessive blue genes.

What Size Will Your Baby Be?

It's difficult to tell what size a baby will be since a newborn's measurements don't necessarily predict their future height and weight. Many factors can influence size at birth, including the pregnant parent's diet and health conditions, such as gestational diabetes, says W. Gregory Feero, M.D., Ph.D, a family physician and special advisor to the National Human Genome Research Institute of the National Institutes of Health.

More than 100 genes code for height, and regardless of a baby's initial length, they will probably grow to their genetically predisposed stature. The exception is kids who have poor nutrition and little physical activity, as they tend to be shorter despite their genetic potential, says Dr. Starr.

Parents can make a rough estimate of their child's future height by using their own. For children who are born female, subtract 5 inches from their father's height and average that number with the other parent's height. For children who are born male, add 5 inches to their mother's height and average that with the other parent's.

Another way is to simply follow a child's growth curve. "If [they're] consistently in the 50th percentile for height and weight, it's likely [they'll] be close to that as an adult," says Begleiter. Of course, it can always change.

Which Parent Will a Child Look Like?

Sometimes children end up looking exactly like one parent, or even closely mirroring a sibling, and sometimes they don't resemble anyone in the family. It's all entirely possible.

Kids share 50% of their DNA with each of their parents and siblings, so there's plenty of room for variation. If siblings end up looking alike, the mix of genes they inherited was similar. But each child may also get instructions for different features: A firstborn child may have one parent's lips, while the youngest may get their lips from the other parent.

In fact, a child's bone structure won't be set until in their 20s because so many genes are involved, including those for growth, bone development, and fat deposits. Until then, parents just have to sit back and enjoy the slow reveal.

Can a baby look like the father and not be his?

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How can you tell if the baby is yours without DNA?

What determines which parent the baby looks like?