My first instinct is to reply: actually, you can do this, in any job! You have a legal entitlement to shared parental leave in the UK, so if you want to take it your employer can't refuse. (Even the rules on qualifying periods are surprisingly lenient.)

Of course, this isn't what they mean. I think what people mean by this comment is some combination of:

1. "My employer would find it difficult to get someone to cover my job for six months";
2. "Taking six months off might negatively impact my career";
3. "The culture in my workplace wouldn't be supportive";
4. "No one has ever taken paternity leave before in my company";
5. "I'm subconciously using my job as a reason to avoid seriously contemplating taking paternity leave".

It's revealing (but not very surprising) that this comment has only ever been said to me by men, never by women. Yet at least 1. and 2. apply just as much to women taking maternity leave. (No doubt 3. too in some workplaces.)

I'm sure the people who've said this to me didn't intend it, and wouldn't defend it. But implicit in what they said is the view that it's acceptable or inevitable that women will take a career hit when they have children. Whereas for men this is reason enough not to take paternity leave.

It shouldn't be acceptable or inevitable, for either gender.^{11 1}To be clear, because I'm sure a few people are going to misconstrue this: I am not in any way criticising people who choose children over career. (Indeed, the opposite bothers me far more.) I'm saying it should be a genuine choice.

As reasons not to take paternity leave when you wanted to, 4. and 5. strike me as rather sad. The most common reaction I've had when people have discovered I'm taking paternity leave has been: "I wish I'd done that."

Is academia more open to paternity leave (or parental leave in general) than other careers? On one level, yes.

UCL (my current employer) has been completely supportive, even though I moved from Cambridge to UCL only a few weeks before K     was born. In fact, UCL's thinking on this was way ahead of mine. They have a very sensible policy of requiring everyone to submit a case for promotion each year. (This guards against self-confident personality types always pushing for promotion, whilst less self-confident personality types never put themselves forward.) The annual promotion round came up a few months after I moved to UCL. When I suggested that it didn't make much sense for me to apply for promotion a few months after I'd arrived, and a few months before going on paternity leave, the immediate reaction was: "that doesn't make any difference."

This is worlds away from the attitude I heard from one father working in the finance industry, whose employer wasn't even happy with them taking the statutory two weeks paternity leave immediately after the birth.

However, on another level, academia is perhaps one of the worst careers in which to take parental leave. The typical academic career path nowadays involves staying a student four or five years more than your peers to complete a masters degree and PhD, then being employed on multiple, two- or three-year, fixed-term contracts (postdocs), before you stand any chance of getting a normal job contract without a fixed end-date (i.e. "tenure"; or a "lectureship" in the UK, which doesn't technically have the concept of tenure). That final step is the most brutal. According to figures from a 2010 document produced by the Royal Society, whilst 30% of PhD graduates in the UK progress to the postdoc stage, only 3.5% make it through to a permanent position.

So a quick estimate reveals you're likely to be in your early- to mid-20s before you graduate from a PhD, spend five to ten years on fixed-term postdoc positions (three or four postdocs seems to be typical in my field), then hit your early- to mid-30s facing a 96% failure rate at the most demanding and competitive step to a permanent position. This crunch point neatly synchronises with the average age of first-time parents in the UK. No wonder that, according to the same Royal Society document, "science is still seen by many as a highly demanding career that is incompatile with family life." And no wonder that this is so often cited by women as one of the reasons they left science.

It's not all bad. The inherently flexible working hours in academia make arranging work around children easier than in many jobs.^{22 2}Or at least, I imagine it does! Check back in half a year when I've reached that stage. It's generally considered a good idea to turn up for your own lectures. And showing your face at the odd departmental meeting won't go amiss. But the things that take up the most time - preparing lectures, grant-writing, miscelaneous admin - usually don't involve working directly with other people in a team, so can be done at any time of day as long as they get done. (Research, of course, is best done at a time and place that no one can track you down and disturb you!)

So, overall, university policies are very supportive of balancing work and children, and the job flexibility is conducive to achieving this. But the career structure makes taking parental leave a big risk. The policy at every university I know of is that parental leave must be taken into account in hiring decisions. But talk to any woman in science, and you'll hear stories of outrageous (even illegal) interview questions asked by some dinosaur faculty member about maternity leave or childcare. (Though the causes of women's striking under-representation in science are complex, and there are many different factors at play.)

It's going to be interesting discovering how this translates from maternity to paternity leave. (My guess: the handful of dinosaurs who think taking maternity leave shows a lack of dedication to science will be incapable of consistently applying their prejudices to men!) I'll report back on any interesting experiences on this blog.

I doubt I'll ever be asked this by anyone outside of academia. I also suspect this question is more likely to be asked amongst theorists than experimentalists. (Though an experimentalist colleague told me she'd been asked something very similar, so maybe I'm wrong about this.) I've certainly never been asked this by anyone who's had children!

Theoretical research is a strange business. All it requires is a pencil and paper. And a plentiful supply of coffee.^{33 3}I work with a very few people who prove theorems using tea, but I have no idea how they do it. There's a recurring fantasy amongst theorists of having food, accommodation and coffee paid for by some other means, leaving one free to do research without having to worry about where the next job/grant is going to come from, liberated from all teaching and admin duties. Gentleman scientists in the 19th century lived out this fantasy. So did Einstein in the early part of his career.^{44 4}Cubitt's principle: Anything citing Einstein as an illustrative example should automatically be treated with suspicion! (On the other hand, if you didn't come from the aristocracy or you weren't a man, the odds were strongly stacked against you becoming a scientist at all before the 20th century.)

The thing is - as anyone who's had children will know! - taking care of a baby is about as far from "taking 6 months completely off" as you can get. Perhaps it's impossible to appreciate this until you do it yourself. I certainly didn't until I was taking care of K     full-time. Talking to other mums,^{55 5}Until very recently when a friend started theirs, I didn't know any other dads taking paternity leave. the word most people use to describe it is "relentless". It's not that there are no breaks. There are, when K     takes a nap. (Vital opportunities to wash and sterilize bottles, prepare food, clear up, have a shower, get dressed, go to the loo…!) But the breaks are on her terms, not mine. You don't get to decide you need a break from parenting for five minutes, and sit down for a cup of tea!

I guess I could get some research done by leaving K     in a bouncer most of the day and ignoring her. (Though she'd be vocally demanding to be shown something new within two minutes - she's not a baby who's happy just to placidly sit around doing nothing for any length of time!) But I didn't take six months (unpaid) paternity leave to ignore K     and work.

So what am I doing writing blog posts? The difference between this and research is that it doesn't require much boot-up time. When K     goes down for a nap (and if I don't have bottles to sterilize, food to prepare, stuff to clear up, etc.) I can fairly quickly pick up a post where I left off, remember what I was in the middle of writing, and write a bit more until she wakes up. Which lets me write blog posts over many, many days, in little bits.

The boot-up time for research is much longer. It takes me at least a couple of hours to get back into a research problem, refresh my memory of the approach I was trying, and where it had led to, before I can start making any new progress on a problem. (Writing up research papers is similar.) By that time, K     has long since woken up!

No, anything but!

So collide two of the great gender inequalities of our times, and reinforce one another.

The gender pay gap in the UK stood at^{66 6}"Stood at" is accurate: over the last decade, the pay gap has decreased by about 4% (give or take a bit, due to changes in the way the statistics were generated over this period). And most of that decrease came in the first five years, with the pay gap almost flat-lining for the last five years. almost 20% in 2015. I.e. on average women working in the UK earn 20% less than men. This is the median figure, including both full-time and part-time employment. That seems the most relevant figure when considering how the gender pay gap interacts with parental leave.^{77 7}But note that this figure tells us almost nothing about direct gender discrimination, i.e. women being paid less than men for the same job. When it comes to juggling finances and deciding who will take time off work to care for a baby, what matters is who earns less, not why they earn less. (Indeed, much of the pay gap is due to the much higher proportion of women working part-time.)

Einstein's field equations of general relativity are notoriously difficult to solve because, to quote John Wheeler: "matter tells space-time how to curve; space-time tells matter how to move". The parental-leave-field-equations seem to be even harder to solve: the gender pay gap promotes an unequal division of parental leave; the unequal division of parental leave promotes a gender pay gap.

At the risk of fomenting marital strife, and taking as given that this is a personal decision that every couple have to make for themselves, this strikes me as just as unfair as men refusing to take on any childcare duties. There's no denying that having babies has far more impact on women than on men - biology sees to that! But becoming parents is a joint 18-year 30-year life-long endeavor, not a 9-month one. Surely fathers deserve an equal chance to spend a brief few months full-time with their new baby? (With all the thrill, hard work, stress, enjoyment and sleep-deprevation that goes along with that!) Interestingly, in Sweden three months of the parental leave is reserved for the father. (Three months is also reserved for the mother. I'm going to keep coming back to Sweden, as it has one of the most progressive parental leave policies in the world.)

There's another reason to be supportive of sharing parental leave more equally. Child development studies indicate that children fare significantly better on various measures if fathers are also actively involved in bringing them up: "…the results have been remarkably consistent. Children with highly involved fathers were characterized by increased cognitive competence, increased empathy, less sex-stereotyped beliefs, and a more internal locus of control." Another slightly more recent review of the literature backs this up. It's not because fathers are uniquely important, but because having two highly involved carers is doubly beneficial.^{88 8}So though these studies were specifically about fathers, it seems very likely that the conclusions also apply to same-sex couples. (There are also various other, more subtle, positive effects. It's worth reading the full introduction to the Lamb book for the whole story; the complete introduction is available in the Google Books preview.) There's an even larger body of research on the effects of absentee fathers on children. But let's stick to the uplifting side of the equation.

These are not studies of shared parental leave per se. But shared parental leave seems like an excellent way to promote the factors that were studied: engagement, availability, responsiblity, and closeness. That's definitely been my experience.

I'm repeatedly surprised by how many people (and these are mostly people who've had children recently) are completely unaware of the laws on paternity leave in the UK. Sometimes they're vaguely aware that the law changed last year (2015). But in that case, they typically think that was when paternity leave was first introduced.

What S     and I are doing has already been possible in the UK for the last five years. Since 2011, parents in the UK have been allowed to split their parental leave in two, with the mother taking the first part and the father taking the second. (Fathers couldn't take more than six months, and it had to be the second half.)

What changed in 2015 was that this become much more flexible. The details of the new shared parental leave law are extremely convoluted. But, essentially, you now get twelve months in total, which you can split between you however you like. You can even overlap some - or all - of the leave.

Here's an interesting comparison: Sweden introduced gender-neutral parental leave 40 years ago. Nowadays, Swedish parents get 480 days of paid leave. 90 days of that are reserved for the father. The first 390 days are paid at 80% salary. The remaining 90 days are paid at a rate similar to statutory parental pay in the UK (which you're only entitled to for the first nine months anyway). And parents splitting the leave equally get a small, tax-free, daily bonus for 270 days! Swedish dads take 25% of the total parental leave. Less than 1% of UK dads took the additional paternity leave available from 2011.

This is not the 1% shared parental leave statistic widely reported in the media recently, and roundly debunked by Radio 4's More or Less programme. The shared parental leave scheme introduced in 2015 is too recent for useful statistics to be available yet. The statistic I'm quoting is for the older additional paternity leave scheme, and it at least measures what it claims to measure. (Keep a wary eye out for more dodgy shared parental leave statistics when the government reports figures in a couple of year's time.)

Incredibly, until 2003 there was no such thing as paternity leave in the UK. That's right: new fathers were expected to go back to work the day after the birth. Until 2011, things weren't much better: fathers got just two weeks total, to be taken immediately or shortly after the birth.

Perhaps it's not surprising so few people realise equal paternity leave is an option.

(I should clarify that no one's ever said this to me about paternity leave per se. But I have heard this said about childcare in general by people who didn't know I was taking paternity leave.)

This comment is a bit behind the times…by about 20,000 years. It hasn't been true since the invention of baby bottles, which dates back at least 3000 years, and very likely much further still to soon after the invention of pottery. Since the invention of breast pumps in the mid 19th century, bottle-feeding doesn't even mean stopping breast-feeding.

Of course, that's not what they mean.

They mean that babies need their mothers in an emotional or psychological sense, rather than a strictly physical sense. It's at least a plausible hypothesis. But it's just a hypothesis, and one that fits suspiciously comfortably with preconceived gender stereotypes. What does the evidence say?

If there was little research on the impact of fathers on child development until the last decade or two, there's even less on fathers as primary caregivers. The odd study I could find doesn't seem to show any negative impact at all. (In fact, that one seems to suggest children benefit from having the father as primary carer, though the sample is far too small to be statistically significant. If it's a real effect, it's probably another instance of the benefit of having two engaged parents. It's not clear from the article, but the study seems to have involved two-parent families where the mother worked, so it's likely the mothers were still very engaged in parenting.)

There are more studies of the effect on child development of the mother not being the primary carer (i.e. children placed in some form of childcare). These have consistently found that the crucial factor is not the identity of the primary carer, or even whether the primary carer is related to the child. The crucial factor is whether that primary carer is responsive, engaged, and emotionally supportive.

In other words, what evidence there is suggests that babies don't need their mothers; they need their carers - whoever they are - to be good parents.

Braver than the 99% of mothers who take maternity leave?