Gender identity is considered more fluid than ever because of the success of the trans movement. But most trans people, just like everyone else, still identify as either a man or a women. For those who feel they are neither – or both – the male-female distinction does not fit. And, for the one in 2000 who are born with indeterminate sex, finding a place in this binary world can be damaging.

So, are there enough genders? We hear from Dr Imran Mushtaq, who works with intersex children at Great Ormond Street Hospital in London; bi-gender vlogger Brin Convenient; Tamara Adrian, Venezuela’s first transgender congresswomen (who wants gender erased from official forms); and the writer Mark Gevisser.

(Photo: Transgender transsexual concept. Credit: Thinkstock by Getty Images)

The richest 10% of Americans earn half of all of income. In Britain, the top 10% hold 40% of all the income. Inequality is not just an issue for rich countries. A billion people have been lifted out of poverty since 1990, and inequality has been rising in many other countries too. So, how much inequality is too much? Many may recoil from such a question - inequality is a dirty word. But this programme isn't about fairness. This programme is about economics – and how far inequality affects growth and prosperity. Presented by Linda Yueh.

(Photo: A woman walks past a poor man. Credit: Getty Images)

The world has a problem. The climate is changing. At least, most people think so. That’s why global leaders have been meeting in Paris to work out a way to deal with the problem. They blame carbon dioxide in the atmosphere, much of it released by the human need for energy, obtained from fossil fuels like oil and coal. But believe it or not the world also has a solution at hand: sunlight. Harvest it where it shines brightest, in the Sahara Desert for example, and you have the ultimate get-out-of-jail-free card: a techno-fix to the mother of all problems. So, our question this week: why don't we solar panel the Sahara? Our contributors include: Gerhard Knies, a German physicist who has developed the idea; Tony Patt, who leads on this issue for the European Research Council; Daniel Egbe from the African Network for Solar Energy; and Helen Anne Curry, a technology historian, from Cambridge University in the UK. Presented by Michael Blastland

(Photo: Sahara Desert. Credit: Getty Images)

The UN forecasts that the number of people living in Africa will double in the next 35 years. Nigeria, the fastest-growing nation, is expected to become the third-largest country in the world by 2050. By the end of the century, almost 40% of the world’s population will live on this one continent. It raises questions about how countries – some of which are already facing big challenges – will cope with twice the number of inhabitants in just one generation. There are fears about the impact a demographic explosion will have on health, society and the environment. But others say Africa’s population boom could turn out to be a good news story. How will a population boom change Africa? Ruth Alexander investigates.

(Photo: Onitsha-Asaba Highway. Credit: Pius Utomi Ekpei/Getty Images)

Many claim that ‘Islamic State’ is the ideological offspring of Saudi Arabia; that the strict form of Islam originating in the Kingdom - and the Saudi state's aggressive promotion of it around the world – has fostered terrorism. Saudi Arabia is also accused of funding IS, either directly or by failing to prevent private citizens from sending money to the group. But what is the evidence for these claims? Our expert witnesses include: a former recruiter for Al Qaeda who explains what motivates jihadists; an Islamic law scholar who explains the little-understood beliefs of the so-called Islamic State; and a Saudi government official who says, far from aiding IS, his country is at the cutting edge of countering it.

Presenter: Helena Merriman

(Photo: Kingdom Tower in Riyadh. Credit to Shutterstock)

Imagine waking up one morning to the sound of a helicopter overhead. You look out and see that packages are being dropped in front of the homes of everyone on your street. You race downstairs, and tear open your package. Inside? Exactly $10,000 in new bills. A gift of freshly-printed money from your government – no strings attached. What would you do? Economists hope you would go out and spend – and that your spending would help kick start the post-industrial economies which many fear are grinding, inexorably, to a complete halt.

We explore whether so-called “helicopter money” (more likely, money would simply be wired to your account) really is a solution to the problem of a low- or no-growth future. Our expert witnesses include: Adair Turner, the former head of Britain’s Financial Services Authority, who is prescribing just such economic medicine; Mohamed El-Erian, chairman of President Obama's Global Development Council; Professor Barry Eichengreen of Berkeley University in the United States and Richard Koo, formerly of the Federal Reserve Bank of New York and an economic advisor to successive Japanese governments. Presented by Linda Yueh.

(Photo: Helicopter at G7, Credit: Getty Images)

In November the US Drug Enforcement Administration issued its Drug Threat Assessment. Mexican ‘transnational criminal organisations’, it said, are the primary suppliers of heroin, cocaine, methamphetamine, and marijuana to the United States. Drugs – the DEA says – are killing 46,000 Americans a year. But between Mexico’s criminal enterprises, and their clients, is a vast expanse of difficult geography and an international border. So, how do cartels get drugs into the US? The Inquiry hears from serving US law enforcement personnel tasked with intercepting drugs shipments. Their stories – of tunnels, “narco-subs” and complex criminal networks – are astonishing.

(Photo: Narco-Submarines, Credit: Reuters)

We first asked this question over a year ago. So far, the answer has been no. The attacks in Paris killed 129 people. The day before that 43 people died when suicide bombers hit Beirut. Nearly two weeks before that a Russian passenger jet exploded over Egypt, killing all 224 people on board. The group calling itself Islamic State has claimed responsibility for all these attacks. If true, in two weeks, they have killed almost 400 civilians, in places way beyond the areas they control in Syria and Iraq. And they would have managed all that while being challenged on the ground by Kurdish fighters and bombed from the air, by coalition war planes, over 8,000 times. Can IS be defeated? We have gone back to the same expert witnesses we met the first time we asked the question. Now, over a year later, we want to know whether their answers have changed.

(Photo: Female Kurdish soldier on the frontline against ISIL, Credit: Getty Images)

New research suggests plants might be capable of more than many of us might expect. Some – controversially – even describe plants as “intelligent”, or even “sentient”. So, this week, we’re asking: have we underestimated plants? Our expert witnesses include an academic studying how networks of trees communicate through what she describes as a “wood wide web”, and the pioneer who is using plants to develop robotics.

(Photo: US-Fall-Shenandoah, Credit: Getty Images)

Syria’s cultural heritage is being attacked from all sides - the Assad regime, opportunistic looters, opposition forces, Islamic State fighters and even Russian air strikes. Ancient sites like Palmyra have been destroyed, and it is feared that hundreds of precious valuables have been smuggled out of the country to be sold on the international art market. Is it too late to save Syria’s antiquities? We speak to experts including the specialist trying to recover stolen items being sold on the global antiquities market, the volunteer organising a kind of archaeological resistance inside Syria, and the team reconstructing the country’s historic sites using technology.

(Photo: Baalshamin detonation, Credit: AP)

Mohammed Akhlaq’s murder shocked India. A mob broke into his house last month and beat him to death. They believed a rumour that Mr Akhlaq, a Muslim, had broken a Hindu taboo by slaughtering a cow. We find out how the cow became such a political animal and look at whether Hindu nationalists are feeling bolder in today’s India.

(Photo: An Indian woman sprinkles yoghurt paste onto a cow's forehead. Credit:Getty Images)

Rhinos are in trouble. The ancient Sumatran rhino has just been declared extinct in Malaysia, following the fate of black rhinos in West Africa in 2011. Central Africa's northern white rhino has been reduced to four - yes, four - animals, and conservationists say the more plentiful southern white rhinos are under unprecedented attack from poachers eager to sell the horns to Asian and Arab buyers. This week The Inquiry hears four very different answers to the question: How do you save the rhino? Experts include Namibia’s first female dangerous game professional hunter and one of China’s biggest celebrities and campaigner, Yao Ming.

(Image: A baby rhino and an adult rhino. Credit: Getty Images)