“You’ll need this,” said The Doctor handing Jean something that looked like a small tennis racket except that it had a button on the side. She pressed it and the racket buzzed strangely.

“Don’t touch the lattice,” The Doctor told her two seconds too late. She yelped and dropped the racket as a mild but unexpected electric shock coursed through her hand.

“What the hell IS this thing?” she demanded.

“Personal bug guard,” The Doctor answered. “It emits a signal that makes anything that crawls or flies keep away from you, and in case anything doesn’t get the message you can swat them with it.”

“We’re going somewhere with insects?” Jean guessed.

“Yes.”

“Where?”

“It’s a surprise,” The Doctor answered. “But bring the bug guard.”

Jean was sensibly dressed in light slacks and t-shirt with walking shoes. She had been told they were going on a trek and this had been the outfit the TARDIS wardrobe had presented when she went to change. She assumed from that and the bug guard that they were visiting somewhere tropical.

And so it seemed when they stepped out of the ambient temperature and humidity of the TARDIS into the steamy jungle where Jean’s t-shirt began to stick to her skin after a few seconds. Brushing sweat from her eyes she looked up at the canopy of green with spears of sunshine piercing it here and there. The trunks of the trees were straight and tall, each one about a metre in diameter at the base.

There were plenty of insects, and though she wasn’t especially squeamish about such things Jean was glad they were keeping a distance. The sight of a two foot long millipede winding its way around the base of a tree and a scorpion the size of her foot were startling. The more she looked at the leaf litter beneath her feet the more it seemed to be alive with crawling, burrowing things and the air above and around her was filled with flying things.

“Where are we?” she asked. “This must be somewhere alien… or the Amazon…. Or the Malayan jungle….”

The Doctor grinned enigmatically.

“What?” she grinned back despite herself. “So… where ARE we?”

“Glasgow,” he answered.

“Don’t be silly,” Jean answered. “Even in the hothouse at the Botanical Garden there’s nothing like this. Unless….” She looked up at the canopy again. “Is there some planet CALLED Glasgow or something? Like that Barcelona place where you kept telling that stupid joke about dogs and their noses.”

“No, it’s not a planet called Glasgow,” The Doctor assured her. He waited for her to work it out. He knew she would, sooner or later. She was smart, and she knew history. It would come to her.

“Wait a minute,” she said. “Glasgow… three hundred million years ago… give or take… was on the equator, because a whole lot of continental drift still had to happen before Europe was recognisable… and it was part of a huge forest that covered the land mass from Ireland to Mongolia. Except the trees weren’t exactly trees, they were huge ferns like….” She searched her memory. “Giant club moss.”

“Lepidodendron,” The Doctor said.

“You can get pills for that,” Jean responded, but she knew he was giving the proper name for the extinct species of plant. He could also have used words like arborescent, meaning tree-like, to distinguish them from actual trees.

“Don’t tell me,” she added. “We’re standing in what will be Victoria Park in three hundred million years, where the petrified stumps of some of these plants are preserved.”

“Well, maybe not EXACTLY there,” The Doctor admitted. “Getting the TARDIS to work out a location that has altered its latitude so drastically is complicated enough. We’re definitely around Glasgow, though.”

“Not bad!” Jean’s grin widened. “Not bad at all. So are we here for a Jurassic picnic or something more important, like aliens messing with the flora and fauna?”

“Jurassic picnic,” The Doctor answered. “Well, not exactly since the Jurassic era is still millions of years in the future. We’re in the late Silurian period of the Palaeozoic era just before land flora began to fully diversify. But that sort of thing, definitely. As for aliens… if I caught any of them here without a permit they’d get sent away with a flea in their ears – or whatever orifice sufficed and providing that the flea wasn’t vital to the ecosystem. Messing about with proto-planets is banned by several intergalactic treaties, most of which I’ve signed. Which reminds me - the swatting function of the bug guard is only for use in extreme circumstances. The less fauna you directly interact with, the better.”

“Why?” Jean began, then the answer presented itself to her. “Ah… it’s that stepping on a butterfly thing, isn’t it? I might kill a two foot long millipede that turns out to be the direct ancestor of the Prime Minister.”

“The Prime Minister’s ancestors were a sort of amphibious eel from the planet Electi,” The Doctor replied. “But don’t tell him I told you.”

“I’d have a bunch of other things to tell him about ‘cutbacks’ before I told him he’s descended from a slimy fish,” Jean answered. “But I am right about the butterfly thing?”

“Yes. Hence the fact that everything we might tread on is burrowing or scurrying away as we walk - minimising the impact on the environment.”

That satisfied Jean’s curiosity. She walked beside The Doctor in a bug free zone, watching the larger than life fauna from what she considered a safe distance and marvelling at the sheer alien-ness of her own planet this far back in time. She knew generally about continental drift. Back in lower secondary school the idea that Scotland had once straddled the equator as the landmasses that would one day make up Europe travelled north by a fingernail’s length per year had boggled her imagination. She had gone on a school trip to see an ancient coal seam where these huge plants and the animals that scurried about the undergrowth had lived and died and been compressed into carbon. She had visited the Fossil Grove in Victoria Park on one of those school outings, too. She remembered being asked to imagine forests of giant ferns with stalks up to thirty metres high, and she was bright enough to manage that while looking at the grey, petrified stumps and roots.

Never in her wildest dreams did she imagine standing here among the living, buzzing, crawling leaf litter with the canopy, green and alive, above her head.

“The fossil grove was preserved when lava from a volcano flowed around what was left,” she pointed out. “That’s not… imminent, is it?”

“Not for at least a hundred million years,” The Doctor assured her. “About the time when Edinburgh and Aberdeen were really dangerous places to be.”

“Doctor, you were never in Edinburgh city centre on a Friday night,” Jean responded. “It’s always been a dangerous place to be.” But again she knew the history. Edinburgh Castle was perched on top of an extinct volcano that had shaped the landscape long before her time. Aberdeen, likewise.

“We could, in theory, walk all the way to the islands,” she said. “They wouldn’t have been islands back now. Bute and all the other isles are fragments that were cut off by rising sea levels after the last ice age.”

An ice age was impossible to imagine in the sweltering heat of this ancient jungle, though. Her mind slid from the very idea as she watched a spider with legs as long as her arm and as thick as her fingers wrestling with one of those millipedes halfway up one of the treelike trunks. She had a feeling the spider was going to win the fight. That was nature doing what nature was meant to do. Nothing for her to worry about.

“There are no mammals or reptiles, yet, are there?” she asked as they walked on leaving the life and death struggle behind. “That’s why the insects are so big. They have no natural predators except each other. It’s… only later… that they become smaller and able to hide in the undergrowth.”

“Ten out of ten for observation and deduction, Miss Ferguson,” The Doctor said with the air of one of her favourite secondary school teachers, Mr Latimer, who liked it when the students thought for themselves. Mr Latimer would have liked it here. He was a man who could tell ladybird species apart at a glance.

A foot long ancestor of the ladybird flew by and landed on a piece of leaf mould nearby. Jean counted the yellow spots on the greenish-orange carapace before it flew off again. One up on Mr Latimer.

The Doctor wasn’t kidding about having a picnic. After an hour and a half wandering in the forest he found a suitable place where a couple of the Giant Clubmosses – or Lepidodendron - had fallen and the race to close the gap in the canopy hadn’t yet been won by those younger plants striving to reach the dizzy heights. He pressed the button on his own bug guard four times in quick succession, which extended its field for several metres, then planted it in the ground before laying out a picnic blanket.

“Great invention. Whoever thought of it should get a prize for saving a million picnics from wasp infestation.”

“He did, but not until the mid-twenty-fourth century,” The Doctor answered. He opened the knapsack he had been carrying and brought out far more delicious food than it could possibly have held. Jean didn’t bother to comment about that, since the knapsack came from the TARDIS. Nor did she let him have the satisfaction of explaining how everything was fridge cool even in the heat of the tropical forest. Perhaps it was invented by the same man who liked wasp free sandwiches.

Jean enjoyed the picnic lunch, anyway. So did The Doctor. The whole trip was a pleasant interlude so far with nothing, not even mosquitoes, trying to eat them.

The bug-free perimeter was all the more obvious while they were sitting in one place. Flights of insects of all shapes and sizes went around their zone rather than through it. Jean recalled that certain insects learnt the flight paths from their hives or dung heaps or whatever they had and never diverged from them. She wondered what this might be doing to their internal navigation, but only as an idle thought. They were leaving no other mark on this fantastic place.

They finished their picnic and moved on. The Doctor had a small compass and showed her the direction they were going. She recalled the geography of Glasgow. If the TARDIS had been even close to the future location of Victoria Park, then something else was missing as well as the children’s play area.

“No river. We should have come to the Clyde by now.”

“That’s a long time away,” The Doctor told her. “A lot of continental drift and a couple of ice ages.”

“Yes, of course. This really is strange, knowing where I am, and yet at this time, insects are the only land creatures in existence, even trees as I know them haven’t evolved. Nothing recognisable has come into being. It’s almost frightening to think about.”

“Of course, you’re making the same mistake people made before Darwin’s theory became commonly accepted,” The Doctor said. “You’re thinking of the world as you know it as the finished version. But the Atlantic Ocean in your time is widening by a centimetre a year and the Pacific is getting narrower by the same rate. Tectonic plates are shifting all the time. One day Europe will split apart at its seams again and drift off in all directions. The Americas will bump into the Far East, Australia will drift north and squash India into the middle of a new Super Continent….”

“Don’t.” Jean stopped him. It was all fascinating, but also a little frightening. Trying to imagine the history of the world from where she was standing right now to as long again after her own time made her feel so very small and insignificant, her life so fleeting and unimportant in the huge scale of things.

“I never feel that,” The Doctor said unexpectedly.

“Feel what?”

“Insignificant in the scale of the universe. When I was eight years old, I was taken, according to the custom of my people, to face the Untempered Schism – a place where all of time and space, all of existence, could be viewed at once. I looked at it… and saw how vast and unending it was… and who I was in relation to it.”

“An eight year old boy… didn’t it make you want to crawl into a hole?”

“No… because I was an eight year old boy who was going to be a Time Lord when I was older. I was going to be master of all that infinity. I had nothing to be frightened of.”

“Oh….”

“Except I was frightened. I didn’t WANT to be its master. My first instinct was to run from it. Later, I embraced it, but I still didn’t want to master it… I just wanted to explore it and know it close up, in its wonderful detail, not all at once.”

“I see… I think.” Jean looked at The Doctor and tried to imagine his perspective on the universe, but it was impossible. Her Human mind couldn’t encompass it.

“Better not try,” he told her kindly. “It can bring on terrible migraines. Let’s not worry about all that. We’re having a nice time, aren’t we?”

“Yes, we are,” Jean agreed. “A very nice time. And it’s nice to think that’s the only reason you brought me here… to have a nice time and see something truly awesome without looking for anything sinister and terrible here.”

The Doctor smiled warmly. They understood each other. They continued their exploration of the prehistoric jungle with The Doctor half-jokingly telling Jean which district of Glasgow they were walking through.

Then they both heard his sonic screwdriver’s electronic beep, an utterly incongruous sound in this place where raw nature ruled. He reached for it and examined the tiny LCD display critically.

“Jean,” he said slowly. “You know when you mentioned about nothing sinister or terrible….”

“Yes….”

“I think there is something here… whether it’s sinister or terrible I don’t know… but it doesn’t belong here.”

“Oh.”

“We could ignore it and go and see what Edinburgh was like when the volcano was blowing its top….”

Jean knew that The Doctor was leaving the decision up to her. He would rather dive right into the mystery. But he had promised her no complications.

“We HAVE to find out,” she said. “If it’s something that causes problems in this ecosystem… the butterfly thing….”

“You’re sure?” he asked. “Honestly, volcanoes are more fun.”

“You’re just teasing me now. You know we CAN’T just leave it.”

The Doctor grinned widely and waved the sonic like a divining rod, trying to pinpoint the direction the signal was coming from.

“It’s no more than a quarter of a mile that way,” he said before striding off in his energetic way. Jean had to increase her own pace to keep up with him. He put on an air of mere curiosity about the cause of the strange signal, but she suspected that he was worried.

And perhaps he had good reason to be. They came into another clearing, one much like the one where they had eaten their lunch. But the giant club moss trunks hadn’t been felled this time by natural events. Instead they had been cut down by a small space craft crashing through the canopy and half burying itself in the ground.

The Doctor viewed the devastation from the edge of the clearing before stepping closer. Jean felt a little reluctant to follow, but she knew she had to.

The ship had cracked open like an egg on impact. The occupants, three of them, had been killed instantly. Their bodies were still strapped into their seats. They had been a reptilian-humanoid race of some kind, but they had been dead so long that their features were obliterated, eyes and softer parts of their faces eaten by insects and decayed by time itself. White bone showed through desiccated flesh under the grey-green remnants of their scaled outer skin and rags of what had once been space suits.

“We could have done nothing for them even if we had arrived at the moment of impact,” The Doctor confirmed. He examined the computerised navigation but it had all been exposed to the humid jungle for too long. he had no way of knowing where they came from or what caused them to crash through the Earth’s atmosphere.

“There will be a ‘black box’ recorder somewhere. I’ll bring that out. Later when we’re back in the TARDIS I will be able to extract the data. I can contact their planet and let their people know what happened.”

“Closure for their relatives, yes,” Jean agreed. “Is that all we can do? Should we try to bury them or… is it best to leave things as they are?”

Deep beneath the modern Glasgow of the time, in the coal seams the city was built upon and fuelled by, the remains of a crashed space ship and its alien occupants would be fossilised. The millennia of heat and compression that turned the giant club mosses into that coal would crush the metal and distort the organic remains until they were unrecognisable. Nothing to disturb Human understanding of the past would ever be found.

“Yes,” The Doctor agreed. “Leaving them be is the best thing.” He stepped back from the crashed ship and its ill-fated crew and bowed his head for a few moments. Jean did the same. Perhaps she ought to have prayed, but that seemed a difficult thing to do when she was standing in a jungle that existed billions of years before theologists believed the events of Genesis to have taken place. The Doctor’s non-specific gesture of respect fitted much more easily.

Jean waited outside while he found the ‘black box’. She knew the poor dead people couldn’t do her any harm, but she felt a little bit squeamish about being near them.

Then she saw something that redefined ‘squeamish’. She couldn’t suppress they yelp of disgust when she saw the mass of writhing, squirming flesh crawling around the edge of the crashed spaceship. When she forced herself to look closer, she saw that it was hundreds of individuals rather than one large animal, but that made it worse, somehow.

They looked, in a disgusting kind of way, like overcooked pasta shells with tongues that pushed in and out, tasting the air. They had the same pallid hue and the same texture, but they clearly were a kind of living flesh.

“Ugghhh,” she shuddered and backed away as The Doctor emerged from the ship. He noticed her expression and turned to see what had bothered her. He, too, found the creatures repulsive, but he drew closer, adjusting his sonic screwdriver to scan them.

“Uohoh,” he said.

“Uohoh?” Jean queried.

“These aren’t indigenous,” he explained. “I think….” He scanned again and looked at the data critically. “I think they evolved from the bacteria contained within the stomachs of the crash victims… every organic being has bacteria… what the yoghurt advertisers call friendly bacteria. When the intestines were exposed in the crash, these bacteria….”

Jean nodded. She got the idea.

“It’s… a natural thing, then… in a revolting sort of way… part of the decay process….”

“Yes, and no,” The Doctor replied. “This is a new, unique species that has evolved in the warmth and humidity of this fertile young world. It clearly has no natural predators – perhaps it has some scent that wards off the creepy crawlies of the jungle… it looks as if they feed by osmosis, taking nutrients from the air itself… but….”

“But?”

“But who knows what these might yet evolve into,” The Doctor continued. “This is bad, very bad. This is a species that shouldn’t be here.”

He began adjusting his sonic screwdriver again. His face was tight and worried, and at the same time regretful.

“Exterminating a new species, one that hasn’t even begun to fully evolve, fully explore its potential… this is possibly the greatest crime in the galaxy. It’s genocide… it’s… loathsome. But….”

“You’re going to destroy them?”

“I have to. Otherwise Earth’s evolution may be catastrophically altered.”

“Doctor….” Jean looked at the disgusting creatures writhing around the base of the crashed ship then reached out and pushed the sonic screwdriver away. “Doctor, HOW did the Prime Minister come to be descended from a slimy fish from Electrolux or whatever it was you said?”

“The people evolved from the fish on their own planet,” The Doctor said. “And had become technologically advanced while Europe was still in the Dark Ages. By the nineteenth century they were exploring the galaxy and settling among species they outwardly resembled, inter-marrying, integrating and becoming native in all respects.”

“Just like any immigrants in a new place,” Jean remarked. “So… Doctor… what if that’s what these things are? What if destroying them is the WRONG thing to do. What if they’re the ancestors of Alex Salmond or somebody?”

“That’s….” He was about to rubbish her theory, but he knew he couldn’t. It made absolute sense. Earth was still a mixing bowl of ingredients. These strange life forms grown from an alien bacteria might just be the necessary spice for the final pudding.

The metaphor stuck in his throat. He didn’t share it with Jean, but he put his sonic screwdriver back in his pocket.

“Come on. We’ll go this way. It’s a more direct route back to the TARDIS. Let’s not dawdle. The sooner we sort this out, the better.”

“I don’t dawdle,” Jean protested, but he barely heard her. He was off at his usual pace with his daddy-long-legs gait and his elbows everywhere. He didn’t talk very much. He was still clearly worried, not only about the fate of the world, but about his own part in it.

“Is it REALLY genocide if you destroy those creatures?” Jean asked. She was the one who stopped him doing it, though her reasons why were still a little confused in her mind. “Isn’t it just… pest control?”

“There are beings out there in the universe who think destroying humanity is ‘pest control’,” The Doctor answered. “It’s all about perspective. And… yes, it is genocide. And that’s a terrible thing… and I don’t want to have to do it again.”

“Again?” Jean looked at him curiously, but The Doctor wouldn’t or couldn’t explain that remark. The look in his eyes was deeper than any she had ever seen before. A lot of the time she had spent with him he was a court jester, a juggler, a not too competent acrobat and she was never certain what to believe when he told tall stories of strange people and strange places.

Even in the face of danger he laughed and joked and quite often defeated the enemy by hitting it in its pride rather than its heart. Being made a fool of hurt them more than actual wounds.

At other times he COULD be serious. There were some things he never joked about. Daleks, the Time War, Cybermen… three things he had spoken of only in reluctant phrases in dark moods.

But she had never seen him so serious as he was now, faced with the prospect of destroying the over-cooked pasta creatures.

“You’ll make the right decision,” Jean assured him. “You always do.”

“Not always,” The Doctor answered. “Not always.”

Again he didn’t elaborate, in fact, he went very quiet and withdrawn as they drew closer to the TARDIS. Only when he stepped inside and closed the door did he speak.

“At this moment, I am determined to go back and destroy the alien creatures, to commit genocide upon a species with no way to fight back. It is the most appalling thing any sentient being can do. Do you understand that?”

“Yes, Doctor, I understand.”

“Good. Then… if we both understand that, then it is real. When we go forward into the future, it has happened. The creatures are destroyed.”

“Yes.”

He turned the dematerialisation switch. They left Glasgow of three hundred million years ago behind. A few minutes later, they landed in Glasgow in the second decade of the twenty-first century, Jean’s era.

They were outside the magnificent Kelvingrove Art Gallery and Museum, another place Jean remembered from school trips. The grand hall was particularly memorable with a scale model of a spitfire suspended over stuffed animals from all over the world, including a giraffe, elephant, moose and a kangaroo among others. Even as a child, Jean thought she would rather see those animals living in the wild than dead and preserved in a museum, and that opinion hadn’t changed as an adult. Even so, she was curious when The Doctor led her towards the grand entrance built in a spirit of Victorian grandeur.

She could see at once that things weren’t the same as they had been on her last visit. There was no spitfire. There was no giraffe, elephant or moose. The creature that stood where the elephant had been looked more like a fifteen foot high, twenty-foot long, cross between a spider and a crab. In place of the giraffe was something Jean couldn’t even begin to place in any animal genus.

Then she noticed the people. They weren’t Human. They looked as if they had evolved from insects, with hard carapaces on their backs and compound eyes….

Jean didn’t wait to see what else they had that was more insect that mammal. She turned and ran out of the museum. The Doctor wasn’t far behind her. Neither stopped until they were back in the TARDIS.

“Doctor….” Jean began, breathing deeply. “This is the scenario if you kill the pasta creatures?”

“Yes.”

“How?”

“Somehow their absence means that insect life has a far stronger foothold. Insects remain dominant even through the rise and fall of the giant reptiles, and the emergence of mammals. The sentient species on Earth evolves from them.”

“But… but….”

“But that isn’t right,” The Doctor agreed.

He pressed the dematerialisation switch again. They returned to the tropical jungle of Glasgow three hundred million years ago. The TARDIS materialised not far from the crashed ship this time.

“Let me finish the job I was going to do inside the ship,” The Doctor said as they stepped out of the incongruous police box. “You wait outside.”

“Couldn’t I stay in the TARDIS?” Jean asked.

“No. We have to come here and be present in this world, as it is now, even if it is for no more than a few minutes. We have to stamp ourselves onto the alternative timeline where the creatures are left alone. I know now that I have to do that. I’m not going to mess with them… I’m not going to commit genocide.”

He was clearly relieved about that. A weight was lifted from his shoulders and he almost looked his usual self as he emerged from the crashed ship with the ‘black box’ which was actually a pale green mottled colour.

“Now let’s go back to Glasgow in your day and see that giraffe,” The Doctor said.

Jean was half afraid that the giraffe wouldn’t be there, and that the population of Earth would still be descended from insects. The Doctor was certain that it was all right – that they were within the right sequence of events now for Earth’s evolution to be as it ought to have been.

“This time, I had no intention of harming the proto-species,” he assured her. “So the timeline will be correct.

But until she stood in the great hall of the museum and looked at the giraffe and the elephant, and the spitfire overhead, and saw a party of Human schoolchildren paying more attention to their ipods than the exhibits, Jean wasn’t entirely sure that they had got it right.

“Does it mean….” She said when they sat in the museum café drinking coffee. “Does it mean that humans are evolved from those creatures that themselves evolved from bacteria in an alien gut?”

“No,” The Doctor answered. “Humans evolved from the mammalian lifeforms that developed much later in the timeline of this planet. The existence of the proto-species at the time when insects dominated shifted the balance so that other forms of animal life had room to develop.”

“That’s ok, then,” Jean said. “I mean, I know life ultimately started with amino acid chains in the primordial soup, and that’s probably more disgusting than alien gut bacteria, but I really didn’t want that to be where we came from, all the same. I’m… kind of relieved.”

“Yes.” The Doctor was relieved, too, but in his case because he didn’t have to be the agent of destruction for another species.

“How about going to see the Edinburgh volcano, next?” he suggested, pushing thoughts of genocide into the darker corners of his mind and smiling brightly. “From the safety of the TARDIS, of course. No paddling in the lava flow.”

“Sounds good to me,” Jean agreed.